First Rebuild Questions?

[Mgriz]

Thanks to all your help I'm getting closer and closer to a well running bike. Since this is my first rebuild Im a little tentative about riding the bike without everything being relatively perfect. I had some ignition problems, but now that system checks out and seams to be working as intended. Some other symptoms have become apparent and are as follows:

Unstable idle:
Idle raises to 2 or 3k rpm on its own, sometimes after being reved it will only return to 2-3rpm then slowly drop to 1100. I do not think it is the throttle cabling as I have held the throttle against the idle adjustment screw as it was fluctuating. I also checked the intake boots w/ the WD-40 method posted on this site and saw no results, I will try it again with a spray bottle and water just to be sure.

Backfiring:
If I bring the motor up to 3-4k rpm it starts loudly popping rapidly. I also get less violent backfiring on decel.

"Caughing" out carbs:
Occasionally at idle or under decel the carbs will make a "puuuuhhh" sound and the idle will drop.

Slow Fuel Leak:
I have a clear fuel hose and after letting the bike sit overnight with the fuel off there is not longer fuel in the line. There are usually drips of fuel on the bottom of each bowl and it looks as if fuel is seaping out through the bowl gasket area. Could this be just that the bowls are not sealed well? Bad needle valves? Sidestand issue?

3+4 lean:
Plugs 3 and 4 are greyish white in color after idling, 4 more so than 3. I'm thinking that this might be b/c the bike is on its sidestand but Im not sure.

I think thats about it, obviously it needs a carb synch but I think some of these things are beyond that and want to see what you all think about all the issues and what might possibly be causing them.

Additionally, I know that my compression won't be great until it gets broken in a little. Should I be okay riding this bike around in its current condition? I have ridden it around in 1st, it feels strong... no bogging or surging below 5k rpm.Thats a long post, sorry... thanks for your input.

 

[mark]

Just about all of your symptoms (popping, plug color etc.) indicate a lean mixture condition, especially the slow return to idle. You're on the right track checking your intake manifold boots, but it could be caused by incorrectly adjusted pilot air screws, mixure screws etc. pods or other airbox alterations.

I assume you have a stock airbox and stock exhaust?

Your leaky carbs could be worn float needles, incorrectly adjusted or sticking floats, or bad o-rings in your carb. All of your float gaskets could be bad but in my experience they have to be real bad before they leak much. Leaks can be at the gas "T's" as well that give gas to each carb.

You'll have to ride it a little bit to test your adjustments, that won't hurt anything. Riding your bike really lean for a long time can burn your valves ....test riding though shouldn't be a problem.

Are your valves adjusted correctly following your rebuild? That makes a big different too when it comes to the carb synch.

 

[jgordon]

Congratulations on your first rebuild... Here's the thing..What you are describing should not be happening. You need to go back to the basics and check everything real carefully ( Floats, Timing, Valve adjustments ect.,ect )

Check and make sure that the bolts are tight at the exhaust pipes....

Just give it a real good tune-up and you will find the little " Ghosts " that live in your motor now.

I will probably get some other comments about this but in general the new rings that are out now need very little break-in ( You need a good cross hatch pattern on your cylinders ). I would just ride it normal for the first 100 miles or so before you really lay down rubber (-:

 

[nabrams]

The bottom line: With these CV carbureted bikes, the pressure situation at any point before (airbox), after (exhaust) or in between (boots connecting carb-to-engine and airbox-to-carb) can and will affect the bike's performance. Obviously, the air fillter element itself must be OK as well.
I had leaks at all of the above places that took me weeks to find and seal. I was surprised at what a huge difference they made.
The point where the pipes join the head will appear to be just fine when in fact it is leaking slightly - make sure you have brand new exhaust gaskets and that you've torqued those bolts properly.
Very minor leaks at the boots may not be detected with the "mist spray" test.
Leaking carbs and/or fuel lines/connectors may be leaking at a rate that is fast enough to lean the mixture enough to cause what you describe.

Keep at it. You'll work it out.

 

[Mgriz]

Thanks guys and sorry I should know by now to post the details on my bike. It has K&N pods, Yoshi Exhaust, Yoshi Stage 1 cam, DJ Jet Kit, DYNA-S, DYNA 3 Ohm Coils. I rebuilt/chem dipped the carbs, the pilot is set at 1 1/2 turns out, the air at 1 3/4. Valve clearence is perfect and the timing is as good as I could get it without a strobe light. I think my next action will be to remove the carbs again and go through them once more. What is the best way to set up the air and pilot screws. I feel that screwing them both all the way in and then out from there isnt very accurate. My fuel T was leaking but I fixed that w/ orings, I have all new gaskets. If its the needle valves can I get away with just ordering the needles or do I need the entire assembly (Z1 has the needles alone for a reasonable price)? Will a leaking header cause a lean condition? Anyway, thanks again for your help.

 

[mark]

I might re-submit this thread so that the guys who are good with re-jetting and carb work can help you. Start right away with the modifications you have have made to your bike. Stock settings will never work with the stuff you have, re-jetting will be a virtual certainty.

Now I'm sure you are way to lean!

 

[Guest]

Floats

Floats

Sounds like you need new seats and valves. Also, check your float adjustment, not at the hinge but where it steps down. Are you sure your not off a tooth on your cams?

 

[Mgriz]

Sounds like you need new seats and valves. Also, check your float adjustment, not at the hinge but where it steps down. Are you sure your not off a tooth on your cams?

Darn, thats expensive...Im 98% sure that cams timming is set correctly but triple checking won't hurt.

I have my DJ jet kit, air screw, and pilot screw set according to the recommendations made by some of the jetting gurus here. Im aware I'll need to do some fine tuning to get it to run well with all of my modifications but I'm not sure if I am at that point yet. I'll go though everything again...

Remove carbs, take bowls apart, reset float hieght, reset air and pilot screws. Should I lubricate the slides or any carb parts while they are apart?

Check cam timing

Make sure there are no vacuum leaks.

Is there anything else I'm forgetting that I should be keeping an eye out for?? Thanks again for all of your help.

 

[Guest]

I was referring to the float needle valve and seat, sorry I was unclear. Wipe off the slides with carb cleaner sprayed on a towel. DO NOT get any on the diaphragm, it will wrinkle and get ruined, and you think float needles and seats are expensive! Soak carb bodies in berrymans carb dip with all o-rings, gaskets, floats and rubber of any sort removed. Spray all holes with carb cleaner with straw. DJ kits are usually lean on the needle you might want to try to raise it one notch from their directions. You do have the rubber cap over the pilot jet, right? I'm more familiar with CV carbs so I hope this helps. I think your idle adjustment screw is opposite of mine.