B
BassCliff
Guest
Hi,
I found this page on some guy's website. Have a look at the VM Carb Tuning link.
I found this page on some guy's website. Have a look at the VM Carb Tuning link.
-
Required reading for all forum users!!!
Welcome!
Register to access the full functionality of the GSResources forum. Until you register and activate your account you will not have full forum access, nor will you be able to post or reply to messages.A note to new registrants...
All new forum registrations must be activated via email before you have full access to the forum.A Special Note about Email accounts!
DO NOT SIGN UP USING hotmail, outlook, gmx, sbcglobal, att, bellsouth or email.com. They delete our forum signup emails.A note to old forum members...
I receive numerous requests from people who can no longer log in because their accounts were deleted. As mentioned in the forum FAQ, user accounts are deleted if you haven't logged in for the past 6 months. If you can't log in, then create a new forum account. If you don't get an error message, then check your email account for an activation message. If you get a message stating that the email address is already in use, then your account still exists so follow the instructions in the forum FAQ for resetting your password.Have you forgotten your password or have a new email address? Then read the forum FAQ for details on how to reset it.
Any email requests for "can't log in anymore" problems or "lost my password" problems will be deleted. Read the forum FAQ and follow the instructions there - that's what we have one for...
-
Returning Visitors
If you are a returning visitor who never received your confirmation email, then odds are your email provider is blockinig emails from our server. The only thing that can be done to get around this is you will have to try creating another forum account using an email address from another domain.
If you are a returning visitor to the forum and can't log in using your old forum name and password but used to be able to then chances are your account is deleted. Purges of the databases are done regularly. You will have to create a new forum account and you should be all set.
M
MisterCinders
Guest
I have studied that dude's site, but the info there doesn't address re-jetting for pods, etc., and the stock specs show no turns for the fuel pilot screw because of the EPA rules, prohibitions on changing it, etc.
Inferring from the different 77-79 specs, the stock screw settings are
Pilot Fuel Screw - 1.75 (1977) - 2 (1977B) turns out. 78-79 give no setting.
Pilot Air Screw - 1.6 turns out.
Multiple posts here recommend air screws be around 2x the turns of fuel screws.
Right now I have the fuel screws at 1 turn out, and the air screws about 2.25 out. That suggests I am too lean compared to the specs.
With dirty plugs/pipes, I cannot confirm the lean mixture from other symptoms. Moreover, trying to understand the performance symptoms leads to lists like this:
The symptoms I get are:
Moreover, the symptoms I think I am finding split across the lean/rich spectrum.
I know that plugs are the real indicator, but I need to scrub/clean them to get a better handle on them.
Inferring from the different 77-79 specs, the stock screw settings are
Pilot Fuel Screw - 1.75 (1977) - 2 (1977B) turns out. 78-79 give no setting.
Pilot Air Screw - 1.6 turns out.
Multiple posts here recommend air screws be around 2x the turns of fuel screws.
Right now I have the fuel screws at 1 turn out, and the air screws about 2.25 out. That suggests I am too lean compared to the specs.
With dirty plugs/pipes, I cannot confirm the lean mixture from other symptoms. Moreover, trying to understand the performance symptoms leads to lists like this:
My comments above in red
The symptoms I get are:
- popping from air pods (No. 4) during warm up.
- shaky acceleration off the line and a "dip" (?) in power between idle and >1/8 throttle
- maybe flat acceleration once on the move
Moreover, the symptoms I think I am finding split across the lean/rich spectrum.
I know that plugs are the real indicator, but I need to scrub/clean them to get a better handle on them.
G
Guest
Guest
Sounds like you are generally lean.
Have you replaced the main jets yet?
Have you searched the forum for other peoples settings with your mods?
Forget about the stock specs.
Have you replaced the main jets yet?
Have you searched the forum for other peoples settings with your mods?
Forget about the stock specs.
M
MisterCinders
Guest
I have 110s in the mains, and ordered some 120s and 122.5s to go up further.
Stock mains are 100 - 102.5.
Changed those based on other info on the forums.
Stock mains are 100 - 102.5.
Changed those based on other info on the forums.
B
BassCliff
Guest
Hi,
It sounds like you are properly equipping yourself, doing the research, obtaining the parts, etc. I'm sure you'll get it sorted out. Sometimes it takes some educated guesses along with trial and error. Keep us informed.
Thank you for your indulgence,
BassCliff
It sounds like you are properly equipping yourself, doing the research, obtaining the parts, etc. I'm sure you'll get it sorted out. Sometimes it takes some educated guesses along with trial and error. Keep us informed.
Thank you for your indulgence,
BassCliff
Just for the record, a DJ 138 is approx' the same as a Mikuni 130.
If you over-oiled the pods you'll know it. Typically, over-oiled pods will allow the bike to start and run "OK" up to approx' 1/4 throttle and then further opening will result in severe bogging. I know the K&N oiling procedure/suggestion is a bit vague and can result in over-oiling. I hold the can approx' 6" away and with each pass I hit 3 pleats. The next pass may have a slight overlap, depending on the color I see. Hitting "each pleat" will result in over-oiling in my opinion. A "pass" is subject to how fast you make it. A pass to me is one second to hit the entire length. Maybe a short second??
Jetting rich or lean? I'll say that assuming your bike is in good tune,...valve clearances, ignition timing, good voltage/spark, clean carbs, etc, then your pilot circuit SHOULD be lean right now. You mention some noise coming from the pods that I take as "spitting". Lean condition for sure. You still have the stock #15 pilot jets and your pilot fuel screws are approx' 1/2 turn richer (based on the factory setting of about 3/4 turns though it does vary some). Side air screws should be set for highest idle but you say you can't hear a difference. Right now you have them adjusted out further than is typical. So I think you're lean at the pilot circuit.
Try setting the side air screws to 1 3/4 turns out. Keep in mind the rpm range they can effect is only a few hundred rpm. On your bike the base idle must be at 1,000 to start. If you try to set at an idle of 1,200 or 1,300 as a base then you'll have problems hearing changes or even be able to effect that higher idle in the first place. But for now, just set them to 1 3/4 and then re-test when ready.
Try 1 1/2 turns at the pilot fuel screws.
REMOVE the two floatbowl vent lines if they're still attached. Pod filters effect the bowl venting and compromise fuel flow under some conditions. Removing the lines eliminates/helps greatly to avoid fuel starvation. In my experience pods and the vent lines stiill attached does not work well. Don't try shortening them either. Remove them.
As for your previously mentioned idle problem, are you positive the throttle cable(s) are adjusted correctly? 2-3 mm is good slack on the pull cable. Lighly zero out the play on return cable. Cable routing/lubing must be correct too.
Be sure the vacuum line to #3 is good and not kinked or cracking anywhere.
When properly bench synched, the VM carbs will allow the idle to be manually turned down to the point of a stall. If yours won't allow that then you've done something wrong.
Test the pilot circuit around town. Keep it under 1/4 throttle position to avoid overlap effect by the cut-away and jet needle. Just putt around (after full warm up) for a few miles on level/uphill road. Pull into your garage and don't let it idle long. Check the plugs. Tell us what you see and any performance issues. Keep in mind the jet needle effects things earlier than some think and any carb sputting could be due to a lean jet needle position too.
Easy to tell if the jet needle is contributing to spitting by cruising steadily in top gear at approx' 50 to 60 mph. You're mostly on the jet needle at that point. Weather/temp can have varying effects too on jetting that's not correct.
Typically, 1 position richer on stock jet needles isn't enough for your pipe and pods. 1 1/2 positions or even two positions is much more likely to be needed (if you can get the stock needles to give good results at all). Was your stock needle settings at position 3, the middle??
I think the 120's aren't enough either. Many owners here have had good results with 125's and 127.5.
I see no obvious reason why you can't check the pilot, jet needle and main jet mixing. As long as the plugs aren't oil fouled or carbon stained then just shoot them with a little spray cleaner and wipe off with a rag. Test the pilot circuit at mimimal throttle as I described. Test the needles at solid 1/2 throttle and chop off/check. Test the mains at full throttle and chop off/check. Tell us what you see.
Jetting rich or lean? I'll say that assuming your bike is in good tune,...valve clearances, ignition timing, good voltage/spark, clean carbs, etc, then your pilot circuit SHOULD be lean right now. You mention some noise coming from the pods that I take as "spitting". Lean condition for sure. You still have the stock #15 pilot jets and your pilot fuel screws are approx' 1/2 turn richer (based on the factory setting of about 3/4 turns though it does vary some). Side air screws should be set for highest idle but you say you can't hear a difference. Right now you have them adjusted out further than is typical. So I think you're lean at the pilot circuit.
Try setting the side air screws to 1 3/4 turns out. Keep in mind the rpm range they can effect is only a few hundred rpm. On your bike the base idle must be at 1,000 to start. If you try to set at an idle of 1,200 or 1,300 as a base then you'll have problems hearing changes or even be able to effect that higher idle in the first place. But for now, just set them to 1 3/4 and then re-test when ready.
Try 1 1/2 turns at the pilot fuel screws.
REMOVE the two floatbowl vent lines if they're still attached. Pod filters effect the bowl venting and compromise fuel flow under some conditions. Removing the lines eliminates/helps greatly to avoid fuel starvation. In my experience pods and the vent lines stiill attached does not work well. Don't try shortening them either. Remove them.
As for your previously mentioned idle problem, are you positive the throttle cable(s) are adjusted correctly? 2-3 mm is good slack on the pull cable. Lighly zero out the play on return cable. Cable routing/lubing must be correct too.
Be sure the vacuum line to #3 is good and not kinked or cracking anywhere.
When properly bench synched, the VM carbs will allow the idle to be manually turned down to the point of a stall. If yours won't allow that then you've done something wrong.
Test the pilot circuit around town. Keep it under 1/4 throttle position to avoid overlap effect by the cut-away and jet needle. Just putt around (after full warm up) for a few miles on level/uphill road. Pull into your garage and don't let it idle long. Check the plugs. Tell us what you see and any performance issues. Keep in mind the jet needle effects things earlier than some think and any carb sputting could be due to a lean jet needle position too.
Easy to tell if the jet needle is contributing to spitting by cruising steadily in top gear at approx' 50 to 60 mph. You're mostly on the jet needle at that point. Weather/temp can have varying effects too on jetting that's not correct.
Typically, 1 position richer on stock jet needles isn't enough for your pipe and pods. 1 1/2 positions or even two positions is much more likely to be needed (if you can get the stock needles to give good results at all). Was your stock needle settings at position 3, the middle??
I think the 120's aren't enough either. Many owners here have had good results with 125's and 127.5.
I see no obvious reason why you can't check the pilot, jet needle and main jet mixing. As long as the plugs aren't oil fouled or carbon stained then just shoot them with a little spray cleaner and wipe off with a rag. Test the pilot circuit at mimimal throttle as I described. Test the needles at solid 1/2 throttle and chop off/check. Test the mains at full throttle and chop off/check. Tell us what you see.
M
MisterCinders
Guest
Thanks, guys.
The jet needles were set at the No. 2 position. I moved the clips down (needles up) by two notches.
My vacuum line is good, no kinks.
I will ditch the vent tubes.
I sorted out the idle screw problem with a better bench synch and now have a much better range on the idle screw.
The pods seem to be over oiled. I bought the full K&N cleaner/oil kit, so I may clean and re-oil the pods to tighten that up.
Valves are good, as I just did those adjustments when I rebuilt the carbs.
Last night I soaked the plugs in a little petrol and brushed/wiped them clean. After I fine tune the things list above (pod oil, etc.), I will reset the screws, up the main jets and try some plug chops.
Thanks again for the coaching and advice.
The jet needles were set at the No. 2 position. I moved the clips down (needles up) by two notches.
My vacuum line is good, no kinks.
I will ditch the vent tubes.
I sorted out the idle screw problem with a better bench synch and now have a much better range on the idle screw.
The pods seem to be over oiled. I bought the full K&N cleaner/oil kit, so I may clean and re-oil the pods to tighten that up.
Valves are good, as I just did those adjustments when I rebuilt the carbs.
Last night I soaked the plugs in a little petrol and brushed/wiped them clean. After I fine tune the things list above (pod oil, etc.), I will reset the screws, up the main jets and try some plug chops.
Thanks again for the coaching and advice.
Oh. Just remembered something else you said.
There's no need to oil the K&N pods from the inside. (I believe that's what you said you did.) If you oiled from both the outside and inside then I would think you over-oiled for sure. Just clean them and oil as I suggested.
Another thing. When you clean the pods try to keep cleaning solution from excessively entering the inside of the pod. The K&N pods are designed as a one-way filter. Washing them by dunking or like they're a coffeee cup will compromise their flow over time. Just pour about 1/4" deep cleaning solution in a pan and ROLL the pods back and forth until clean. You can then gently (low hose pressure) rinse from the inside-out. Shake off excess water and let air dry only, no blasts of air. Since you have the cleaning kit the instructions should be there.
As for your jet needle adjustments, two positions richer should at least have you in the ballpark. That assumes that position two from the top as you said is actually the factory position?
And if you're not too sure about removing the floatbowl vent lines then keep in mind that Dynojet even tells you to remove them in their stage 3 jet kit info. In my experience it's necessary to do. And I've never had any issue with dirt entering the ports and causing trouble.
There's no need to oil the K&N pods from the inside. (I believe that's what you said you did.) If you oiled from both the outside and inside then I would think you over-oiled for sure. Just clean them and oil as I suggested.
Another thing. When you clean the pods try to keep cleaning solution from excessively entering the inside of the pod. The K&N pods are designed as a one-way filter. Washing them by dunking or like they're a coffeee cup will compromise their flow over time. Just pour about 1/4" deep cleaning solution in a pan and ROLL the pods back and forth until clean. You can then gently (low hose pressure) rinse from the inside-out. Shake off excess water and let air dry only, no blasts of air. Since you have the cleaning kit the instructions should be there.
As for your jet needle adjustments, two positions richer should at least have you in the ballpark. That assumes that position two from the top as you said is actually the factory position?
And if you're not too sure about removing the floatbowl vent lines then keep in mind that Dynojet even tells you to remove them in their stage 3 jet kit info. In my experience it's necessary to do. And I've never had any issue with dirt entering the ports and causing trouble.
Clean and re-oil the pods, clean the plugs, and follow my screw setting suggestions for the pilot circuit. Test and let us know what the plugs say. Remember that the pilot fuel screws (underneath) can be backed out to approx' 3 turns before they are no longer effective. If you still feel the pilot circuit is lean and the less than 1/4 throttle position plug reads indicate the same then it will be necessary to use 17.5 pilot jets and turn the screws back in to something close to factory (3/4 turn) to start.
Re-reading your post #17 it does indicate you're lean. But with the pods oiled properly will be a better test. Let us know what your tests show. Be careful testing the jet needle and mains as this obviously requires some high speed testing.
Re-reading your post #17 it does indicate you're lean. But with the pods oiled properly will be a better test. Let us know what your tests show. Be careful testing the jet needle and mains as this obviously requires some high speed testing.
M
MisterCinders
Guest
Is 3/4 turns the factory fuel screw setting? I could not find that spec because of the whole 1978 EPA issue. The only spec I saw was the 1977 which called for 1.75 turns. Ofc, that bike also had different main jets, but that should not matter for the idle circuit.
I'll take a crack at Air Screw 1.75, but where should I start the Fuel Screw - 0.75 or 1.5?
Recall this post:
I'm too rich. I'm too lean. I'm too rich. Too lean.
IT'S CHINATOWN!
There is no specific setting for the pilot fuel screws.
Generally, they come from the factory about 3/4 to 1 turn out. That's the most common amount. They are set using an emissions analyzer. Sometimes they aren't set the same for each cylinder. It can vary some such as: 3/4, 5/8, 1, 3/4 for example. They may be all the same or different. Why? Because these screws are the fine tuning for the pilot circuit. The pilot jet regulates flow through a hole and the pilot fuel screws adds a little more fuel through a separate hole. Because of differences in each cylinder you need the pilot fuel screw to fine tune. When I say "3/4" it's an approx' amount commonly used. On an old bike that's had the screws disturbed all we can do is pick a starting point that's fairly common.
You test and adjust accordingly. Without a Dyno all we can do is test ride, using the throttle position that's regulated by the jet we're trying to use.
As for the side air screws, they SHOULD have an effect that you can hear if the carbs are operating correctly. They are to be set using the highest rpm method, just like carbs on older cars have a mixture screw. Since you can't hear an rpm difference I'm suggesting that you set them to 1 3/4 as an approx' setting that's also common.
As for rich or lean on your pilot circuit, all I can say is that pipe and pods effect the pilot circuit greatly. They WILL lean it out significantly. If you have a motor that's tuned correctly and has no compression issues then a bike so equipped and using the stock pilot jets is certain to be lean. It's possible that richer pilot fuel screw adjustments MAY be enough to assist the stock pilots so it's worth a try. Test and find out. If not, then you'll need 17.5 pilots and set the screws back to something closer to stock. Again, test and do what the plugs/performance say.
What signs do you look for regarding rich/lean? Depends on the weather, temp, etc. Generally, a cold motor should need moderate choke to start. Warm up about 1 1/2 to 2 minutes at about 2,000 rpm's should allow you to take off. In a few minutes it should be running decent. The idle may pick up 100 to 200 rpm's from stone cold rpm's but hold that after full warm up. You should be able to let the bike idle a minute or so at 1,000 rpm's and then moderately blip the throttle without seeing a puff of dark exhaust. The idle should return without hanging up. It should idle well. Reasonably smooth. When you decelerate the "popping" shouldn't be too much. Decel' from higher rpm's will result in some popping though it's difficult to tell you over the web how much is acceptable. Popping is a lean condition but you have to remember that the carbs are under the leanest condition when the slides are basically closed (very little fuel entering) but the motor is still buzzing. Also, header pipe leaks will cause more popping.
To go on, the pods shouldn't "spit" out. That's a lean condition. But again remember, running the stock jet needle and/or a too small pilot jet can have that effect. Sometimes, you can get a bike jetted fairly well but something minor like a spit now and then may happen. You may find that trying to richen things a bit can lead to worse problems and you just accept minor problems. Whenever you add parts that make more power and change flow, you have to re-tune and sometimes things aren't perfect.
But you should be able to get the bike running well and the plugs running a decent color. That's why you do all the other tuning first and then the jetting last. If you have trouble at least you know it's caused by the jetting.
Generally, they come from the factory about 3/4 to 1 turn out. That's the most common amount. They are set using an emissions analyzer. Sometimes they aren't set the same for each cylinder. It can vary some such as: 3/4, 5/8, 1, 3/4 for example. They may be all the same or different. Why? Because these screws are the fine tuning for the pilot circuit. The pilot jet regulates flow through a hole and the pilot fuel screws adds a little more fuel through a separate hole. Because of differences in each cylinder you need the pilot fuel screw to fine tune. When I say "3/4" it's an approx' amount commonly used. On an old bike that's had the screws disturbed all we can do is pick a starting point that's fairly common.
You test and adjust accordingly. Without a Dyno all we can do is test ride, using the throttle position that's regulated by the jet we're trying to use.
As for the side air screws, they SHOULD have an effect that you can hear if the carbs are operating correctly. They are to be set using the highest rpm method, just like carbs on older cars have a mixture screw. Since you can't hear an rpm difference I'm suggesting that you set them to 1 3/4 as an approx' setting that's also common.
As for rich or lean on your pilot circuit, all I can say is that pipe and pods effect the pilot circuit greatly. They WILL lean it out significantly. If you have a motor that's tuned correctly and has no compression issues then a bike so equipped and using the stock pilot jets is certain to be lean. It's possible that richer pilot fuel screw adjustments MAY be enough to assist the stock pilots so it's worth a try. Test and find out. If not, then you'll need 17.5 pilots and set the screws back to something closer to stock. Again, test and do what the plugs/performance say.
What signs do you look for regarding rich/lean? Depends on the weather, temp, etc. Generally, a cold motor should need moderate choke to start. Warm up about 1 1/2 to 2 minutes at about 2,000 rpm's should allow you to take off. In a few minutes it should be running decent. The idle may pick up 100 to 200 rpm's from stone cold rpm's but hold that after full warm up. You should be able to let the bike idle a minute or so at 1,000 rpm's and then moderately blip the throttle without seeing a puff of dark exhaust. The idle should return without hanging up. It should idle well. Reasonably smooth. When you decelerate the "popping" shouldn't be too much. Decel' from higher rpm's will result in some popping though it's difficult to tell you over the web how much is acceptable. Popping is a lean condition but you have to remember that the carbs are under the leanest condition when the slides are basically closed (very little fuel entering) but the motor is still buzzing. Also, header pipe leaks will cause more popping.
To go on, the pods shouldn't "spit" out. That's a lean condition. But again remember, running the stock jet needle and/or a too small pilot jet can have that effect. Sometimes, you can get a bike jetted fairly well but something minor like a spit now and then may happen. You may find that trying to richen things a bit can lead to worse problems and you just accept minor problems. Whenever you add parts that make more power and change flow, you have to re-tune and sometimes things aren't perfect.
But you should be able to get the bike running well and the plugs running a decent color. That's why you do all the other tuning first and then the jetting last. If you have trouble at least you know it's caused by the jetting.
M
MisterCinders
Guest
Here is the latest.
Good news - I managed to get the vacuum port screws out with a little penetrating oil. w00t!
OK news - Compression tests on cylinders 1, 2 and 4 came out at about 110 psi dry. Low, but not terrible.
Not so OK news - Couldn't fit the tester into cylinder 3 because of that PO's botched spark plug insert. The larger compression test fitting would not thread into the expanded hole. So not sure what compression for that cylinder looks like. Will pull the head this winter to sort out that plug hole. Probably do a little valve and ring inspection too.
Bad news - Hooked up the vacuum synch gauge (the MotionPro not Carbtune) and cannot calibrate the damn thing. No matter how far I back out the gauge screws, the liquid shoots out of the thing, preventing calibration. I know the CarbTune is better, but did not learn that until after dropping $100 on the MotionPro. So no vacuum synch for me until I pick up or borrow a better gauge tool, or come up with a solution to make this SynchPro work.
Cleaned and re-oiled the pods.
Upped the main jets to 122.5 and the pilot jets to 17.5.
Set the fuel screws to 1 turn and the air screws to about 1.5 turns. Fiddled with them at idle, but still cannot really detect the RPM changes via sound or tach. Best efforts got me to about 1.75 - 2 turns out on the air screws, but I am not really sure of that.
Will take her out to do some plug tests. Should also have a ColorTune in hand soon. Between the two, I will conquer this bloody pilot circuit mix.
Good news - I managed to get the vacuum port screws out with a little penetrating oil. w00t!
OK news - Compression tests on cylinders 1, 2 and 4 came out at about 110 psi dry. Low, but not terrible.
Not so OK news - Couldn't fit the tester into cylinder 3 because of that PO's botched spark plug insert. The larger compression test fitting would not thread into the expanded hole. So not sure what compression for that cylinder looks like. Will pull the head this winter to sort out that plug hole. Probably do a little valve and ring inspection too.
Bad news - Hooked up the vacuum synch gauge (the MotionPro not Carbtune) and cannot calibrate the damn thing. No matter how far I back out the gauge screws, the liquid shoots out of the thing, preventing calibration. I know the CarbTune is better, but did not learn that until after dropping $100 on the MotionPro. So no vacuum synch for me until I pick up or borrow a better gauge tool, or come up with a solution to make this SynchPro work.
Cleaned and re-oiled the pods.
Upped the main jets to 122.5 and the pilot jets to 17.5.
Set the fuel screws to 1 turn and the air screws to about 1.5 turns. Fiddled with them at idle, but still cannot really detect the RPM changes via sound or tach. Best efforts got me to about 1.75 - 2 turns out on the air screws, but I am not really sure of that.
Will take her out to do some plug tests. Should also have a ColorTune in hand soon. Between the two, I will conquer this bloody pilot circuit mix.
Sounds good. Let us know how she runs.
M
MisterCinders
Guest
Took bike out for short trip. Idle is climbing a bit. Need to dial back the air.
In this colder weather, it's pretty hard to diagnose things or even tell when the bike is warm enough to set the idle.
At the dentist now, but will fine tune air and fuel in the lot and chop plugs when I get home.
In this colder weather, it's pretty hard to diagnose things or even tell when the bike is warm enough to set the idle.
At the dentist now, but will fine tune air and fuel in the lot and chop plugs when I get home.
M
MisterCinders
Guest
Ugh. Got the idle tamed. Did some plug tests. They are all over the.map. Including one that is black and oily. FML.
Oil on the plug isn't good. You can't get good combustion when oil's involved so plug reads (for jetting purposes) are useless. You'll have to repair the oil problem as much as I hate to say it. Sounds like you've been busting it trying to get the bike running well but that's how it is with old bikes. Maybe a valve guide seal but I guess you can get to it when you take the motor apart as you were intending. If you still want to ride as is you may be able to get away with it. If that cylinder completely fouls then you'll have to stop or keep cleaning/replacing that plug to squeeze more miles out of it.
Which plug test result is this? At minimal throttle/putting around (pilot circuit)?
M
MisterCinders
Guest
Yes. Just putting around town.
M
MisterCinders
Guest
I only have a couple more rides until snow. Then I'll tear into the top end.
I read your latest posts too.
You read my opinion on the oily plug/cylinder. As for the other plug reads being all over the map, the pilot circuit is VERY sensitive to mixture changes and vacuum issues. More so than the jet needle/main circuits. Just hook up a vacuum gauge and watch the vacuum levels move at factory idle and you'll see what I mean. So relatively minor adjustments at the pilot fuel screws may be all you need.
As for final tuning, you need to vacuum synch to get accurate reads about the jetting and THEN fine tune the jetting. You CAN bench synch and test to get a basic idea of how each carb is mixing. If you have the wrong jetting installed then a vacuum synch won't result in good performance. If you believe you're close (no excessively rich or lean readings) after initial testing then vacuum synch and test again. With reasonably uniform vacuum at all cylinders you can fine tune the jetting.
In your case I would also test the performance at 1/3 to 1/2 throttle to be sure the jet needle positions look good. If they should be too light or dark then you'll have to make jet needle adjustments and that requires a new bench/vacuum tool synch each time you disturb the needles on VM carbs.
Similar threads
