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Overheating problem?

  • Thread starter Thread starter claygs750e
  • Start date Start date
C

claygs750e

Guest
So after a semi complete build of my caf? project, I finally have it running and have been putting back and forth to work all week with no issue. Then I decide to ride an hour away to MotoGP here in Indy and as soon as I get there it dies and would not even attempt to crank. I wait an hour, it fires right up and rode home just fine. There was a lot of stopping on the way there and the longer we stopped the more smoke I would see coming from the vent hose on top of the breather above the engine. Could it be over heating? On the way home I took the highway and once I got home it started back up. The bike has a stage 3 dyno kit, pods, 4-1 MAC exhaust, has been synced using the carbtune and the mixture screws are 1.5 turns out. Also something else I observed is when I painted this engine I used a high temp clear coat and during the sync process I noticed the top part of the engine has yellowed the silver paint. Not sure if it's the paint, or if that part of the engine is getting too hot.


What are some of the things I need to check first? I've not done much engine work besides fresh oil, filter and gaskets all around.

Thanks,
Ned
 
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Adjust the valves for one thing if you haven't. Engine getting hot is normal, including browning the clear coat. Synthetic oil like Rotella is a good hedge against heat since it hold up to heat better than dino oil. Other than that, consider an oil cooler if you want to be real anal.
 
Although it IS possible that the settings are correct, the pilot screws at 1.5 turns might be a little lean.

Since that is the low-speed circuit, it would affect engine heat at idle and low-throttle openings, exactly what you were experiencing on your way there. Add to that the fact that there was minimal cooling air at those low speeds, ...

I would try richening up the pilot screws a bit, and avoiding low-speed traffic.

.
 
Oil coolers are not recommended on this bike. It has friction bearings on the crank rather then roller bearings. An oil cooler could rob enough oil pressure to cause some serious damage.

Smoke coming from the vent tube is telling me you are getting alot of blow back from the cylinder(s) like bad/weak rings or something. Usually with bad/weak rings you would see some blue smoke out the pipes. Burnt gasses are getting by the rings into the crankcase then vent out at the tube in the valve cover. Just like the breather systems on old vehicles before the onset of PVC systems.
 
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I've not seen any blue smoke from the pipes and if I'm just on a short ride I don't see much smoke from the tube. Last night though was the furthest I've been on it and if I sat more than a couple minutes at a light it started smoking a good amount. One thing that I've wondered as well and wasn't sure if it was normal, but when you listen to the motor there almost sounds like a hissing sound like air. Could a vacuum leak be causing the problem and the sound is pretty loud so I'm not sure how to even check for it, or if its normal. I was going to turn the mixture screws out to 2 today and maybe I'm just running too lean.
 
Steve said:
Although it IS possible that the settings are correct, the pilot screws at 1.5 turns might be a little lean.

Since that is the low-speed circuit, it would affect engine heat at idle and low-throttle openings, exactly what you were experiencing on your way there. Add to that the fact that there was minimal cooling air at those low speeds, ...

I would try richening up the pilot screws a bit, and avoiding low-speed traffic.

.
Click to expand...

His 1980 750 does not have pilot screws BTW. ;)
 
I've adjusted the mixture screws, but I can only get it to idle steady at 2k rpms, anything below that it slowly dies on any mixture setting. I currently have it at 2.5 turns out and when I had the problem the other day they were 1.5 turns out. What idle rpm's should I be at when there's no throttle? Is 2k too high?
 
claygs750e said:
So after a semi complete build of my caf? project, I finally have it running and have been putting back and forth to work all week with no issue. Then I decide to ride an hour away to MotoGP here in Indy and as soon as I get there it dies and would not even attempt to crank. I wait an hour, it fires right up and rode home just fine. There was a lot of stopping on the way there and the longer we stopped the more smoke I would see coming from the vent hose on top of the breather above the engine. Could it be over heating? On the way home I took the highway and once I got home it started back up. The bike has a stage 3 dyno kit, pods, 4-1 MAC exhaust, has been synced using the carbtune and the mixture screws are 1.5 turns out. Also something else I observed is when I painted this engine I used a high temp clear coat and during the sync process I noticed the top part of the engine has yellowed the silver paint. Not sure if it's the paint, or if that part of the engine is getting too hot.


What are some of the things I need to check first? I've not done much engine work besides fresh oil, filter and gaskets all around.

Thanks,
Ned
Click to expand...

I have the exact same bike with the exact same problem... I switched to high grade 20-50 oil and bike runs much better. My valves are all in spec and my jetting is spot on now. I think due to the POD filters, more gas going in and the exhaust setup the bike is pretty much to full potential power wise may cause the bike to run hotter than normal. I notice that when in traffic or stop and go the problem is worse, but when crusing around and not hammering the bike it runs great. try the 20-50 oil and see if it helps...

POSt a picture of that thing it looks idential to mine almost.
 

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ericeder141 said:
I have the exact same bike with the exact same problem... I switched to high grade 20-50 oil and bike runs much better. My valves are all in spec and my jetting is spot on now. I think due to the POD filters, more gas going in and the exhaust setup the bike is pretty much to full potential power wise may cause the bike to run hotter than normal. I notice that when in traffic or stop and go the problem is worse, but when crusing around and not hammering the bike it runs great. try the 20-50 oil and see if it helps...

POSt a picture of that thing it looks idential to mine almost.
Click to expand...


Sounds to me it is running too lean yet. Pods will make your bike run leaner not richer. Lean conditions lead to higher engine temps. Have you done a spark plug chop yet? Where are you that you have to run 20-50 oil? I ride in the southwest desert, never needed a 20-50 oil here in the summer.
 
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I would say 2k rpm is twice the speed you should be able to idle at. A little over 1k is preferable.

also sounds like you threw pods on without rejetting; a big no no.
 
I installed the dyno stage 3 kit so it should be jetted properly since I have pods and 4-1 pipes. I just got back from a ride and before I left I had the rpms at a 2k baseline since anything less it seems like it would slowly get lower and lower until it died. While riding if I pulled in the clutch the rpms were steady around 2.5. If I stopped and sit there for maybe 3 mins it would hover at 2rpms and then start to slowly dive to under 1rpm where at that point I would hit the throttle to prevent it from dying and it would be back to 2rpm and repeat. Currently I have the mixture screws at 2 1/4th turn, does it seem like it's still too lean? I've had it at 2 1/2 and it did the same thing. Should I go higher than 2 1/2?

Oh year Eric, our bikes do look identical!

latest.jpg
 
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Live here in NJ had a couple days in the mid 90s with 90% humidity, those are the days bike runs like hell. Whens temps are in the 70s and no humidty bike runs great, after the pods were done I did a Dyno jet kit and spent some time playing this jets, needles and clips. Bike does not stutter, bog, or hesiate at any time, plugs are perfect colored when looked at. If jetting was off it would not be running this good.

Not my daily driver so on excessily hot days instead of sweating and overheating the bike I just dirve to work in AC or in the wrangler with the top off.

ClayGS
Looks sweet!! I plan on hiding battery under the seat this winter looks so much better that way, Nice build!!
 
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claygs750e said:
I installed the dyno stage 3 kit so it should be jetted properly since I have pods and 4-1 pipes. I just got back from a ride and before I left I had the rpms at a 2k baseline since anything less it seems like it would slowly get lower and lower until it died. While riding if I pulled in the clutch the rpms were steady around 2.5. If I stopped and sit there for maybe 3 mins it would hover at 2rpms and then start to slowly dive to under 1rpm where at that point I would hit the throttle to prevent it from dying and it would be back to 2rpm and repeat. Currently I have the mixture screws at 2 1/4th turn, does it seem like it's still too lean? I've had it at 2 1/2 and it did the same thing. Should I go higher than 2 1/2?

Oh year Eric, our bikes do look identical!

View attachment 35844
Click to expand...

An erratic idle is often the result of a poor vacuum sync so you might want to tend to that if you haven't synced the carbs yet.

Koolaid Kid published a technique for proper adjustment of the pilot screws. You might want to dig that up and have a go. Personally, I set them for the highest idle, and if your bike's idle doesn't respond to adjustments made to the pilot screws, I'd set them to 2.5 turns and leave them there.
 
I did just complete the carb sync and all are level using the carbtune. Maybe I will turn it back to 2.5 turns or tweak it using the high idle procedure instead.
 
claygs750e said:
I installed the dyno stage 3 kit so it should be jetted properly since I have pods and 4-1 pipes. I just got back from a ride and before I left I had the rpms at a 2k baseline since anything less it seems like it would slowly get lower and lower until it died. While riding if I pulled in the clutch the rpms were steady around 2.5. If I stopped and sit there for maybe 3 mins it would hover at 2rpms and then start to slowly dive to under 1rpm where at that point I would hit the throttle to prevent it from dying and it would be back to 2rpm and repeat. Currently I have the mixture screws at 2 1/4th turn, does it seem like it's still too lean? I've had it at 2 1/2 and it did the same thing. Should I go higher than 2 1/2?

Oh year Eric, our bikes do look identical!

View attachment 35844
Click to expand...

Just because you installed the Dyno stage 3 kit, doesn't mean it is jetted right. Do some plug chops to verify your lean/rich conditions. When and if everything is right, your idle should be 1,000-1,100 rpms and smooth at that.
 
Spark plug chop? Are you referring to this procedure? http://members.dslextreme.com/users/bikecliff/images/highest_rpm_plug_chop.html

Would I do the highest RPM procedure first, then move on to the plug chop? I've not even heard of this before. Is this procedure the same for the CV carbs as well? Do I need to put new plugs in before starting to know my baseline?When looking at the color of the plugs what am I looking at, the insulator?
 
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Oh god what did I start.

Yeah Clay just follow the directions you found, this is a simple procedure. New plugs are fine
 
Did you replace the intake boots? Did you check them for cracks? Check the engine side. I bet they are toast.
 
chef1366 said:
Did you replace the intake boots? Did you check them for cracks? Check the engine side. I bet they are toast.
Click to expand...

Agree.........high idle or erratic rpms at and just above idle signal leanness, usually through air leaks in the induction system. Tuners often misinterpret the signs when plug chopping, so they enrich the pilot circuit only to cause poor transitioning onto the needle.
 
Or it could be that your starter works fine cold, and after getting hot from the normal engine heat, pukes. Seen it on cars quite a lot over the years.
 
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