Tuning help! Revving up..

[Tron]

Hey all,

So my bike was running a bit rough so I did some tuning..Before, the right side was running hotter and the left side was fouling the plug ever 100kms or so. I realized the valve clearance on both sides was WAY off. The right side seems/seemed to have a sticky rocker as well.

So, I Re-set the cam chain tension, valve clearance, and tried to bench sync my carbs.

I have played around with the syncing so much that it seems like there MUST be something else im missing.

Both sides are running hot, but left is a bit hotter. The right is popping and backfiring a bit, and from idle off the line, the right side struggles a bit. The only other issue is when I shift or let off the gas, the bike revs a bit, and doesnt drop back down.
The throttle cable is new, and not the problem.

ANy ideas?

 

[5twins]

Sounds like you're running lean. Have the carbs been re-jetted for your mods? Looks like you're running straight pipes. Also, you may have some air leaks around the carbs or manifolds.

There's not a whole lot to bench syncing. You either get it right or you don't. Same size "crack" of light under each butterfly is all. If cavemen rode 650s, even they could do it.

 

[Tron]

I will mention, the right side ran great before the tuning..

Its jetted for the pods and exhaust yes.

 

[5twins]

Well, if your manifolds are old, removing and installing the carbs may have done them in, causing cracks and subsequent air leaks where you had none before. With the bike idling, spray some WD40 around the manifolds where the carbs fit in. If the idle speed is affected (goes up or down) or the bike just plain dies, you've got some leaks.

 

[Derek]

Its jetted for the pods and exhaust yes.

Maybe not quite.

Compression?
Timing?
Plug gap?
Coil?
Plug wires?
Air leaks? (Carb boots, diaphragms, throttle shaft seals?)

That's what I got for now.

~ Derek

 

[Tron]

Plug wires are new, plugs are new and are have a nice slight brown tinge, coils are fine, compressions good..

Ill have to check for vacuum leaks next.

One note, can the bolts holding the boots to intake be retapped? One seems to not want to get very tight, which could be causing my problem.

 

[jd750ace]

Sounds like a typical lean rev-up.

 

[KentMoney]

Hey all,

So my bike was running a bit rough so I did some tuning..Before, the right side was running hotter and the left side was fouling the plug ever 100kms or so. I realized the valve clearance on both sides was WAY off. The right side seems/seemed to have a sticky rocker as well.

So, I Re-set the cam chain tension, valve clearance, and tried to bench sync my carbs.

I have played around with the syncing so much that it seems like there MUST be something else im missing.

Both sides are running hot, but left is a bit hotter. The right is popping and backfiring a bit, and from idle off the line, the right side struggles a bit. The only other issue is when I shift or let off the gas, the bike revs a bit, and doesnt drop back down.
The throttle cable is new, and not the problem.

ANy ideas?

Tell use what year carbs you got, what are the numbers for all the jets and needles, and what is the diameter of the headers?

A few things though. You said before that the right side was running hot but that it was carbon fouling. I thought carbon fouling was a symptom of a rich condition, but a rich condition should make the cylinder run cooler. So a bit of a contradiction here.

My understanding is that bench syncing gets you close, but that you need to do vacuum synching as well when the engine is running.

Then you said that the left side is now running hotter than the left and that you got backfiring on the right. That make sense because if the right is backfiring it is likely too rich, which would also explain why it is cooler than the left side. The stumbling off the line on the right side is also indicative of a rich condition.

So, again, tell us the specs on your carb jettings, and also consider things like spark plugs. What are you running? are they cold plugs? are you sure both sides have a strong spark?

 

[Tron]

Alright,

BS38s, 140 main 30 pilots, stock needles,K&N filters, Drag pipes that are baffled

Both sides have strong spark, plugs are BP7ES. Both plugs are coming out at with nice color. Not black.

The jetting is correct. The right side was running great, good plug color, but now is running off. I will be testing for leaks tomorrow, it seems like a logical solution. And hopefully getting lucky at salvage on some boots in good shape.

 

[Derek]

Your jetting does seem adequate, I run a completely free flowing setup and I'm jetted in a similar fashion (can't remember at the moment, but I believe 1-up pilot, 2-up main and stock needle location).


Pull the filters off and see if that helps at all. It won't hurt your bike to run unfiltered for a short bit.

~ Derek

 

[Belle]

Plug wires are new, plugs are new and are have a nice slight brown tinge, coils are fine, compressions good..

Ill have to check for vacuum leaks next.

One note, can the bolts holding the boots to intake be retapped? One seems to not want to get very tight, which could be causing my problem.

Yes. If ya don't have a tap & die set you can get one for about 25-30 bucks at a tool shop (use the metric one, ya can sometimes get a full set sae too for a little more). You'll need larger bolts, I usually get mine from TSC--good enough quality & good enough price. & for the record ya wouldn't be tapping a bolt you'd die a bolt but for a couple of bucks ya can replace a stripped bolt. Just follow the directions that come w/ the tap & die set.