Pops through the exhaust ???

[rickybeaver]

Hey all,my 80 xs1100 special seems to pop through the exhaust when I let off the gas and at low idle.When I hold the gas steady at 1500 rpm's it is rough.After I go beyond that it smooths right out. Would I be correct to assume it needs a carb overhaul or cleaning???? Also is it just mine or are they all hard on gas? Thanks:Rick

[CatatonicBug]

Yep, I'd start with a carb cleaning, just to be certain that's out of the way. However, the main reason for the popping is likely that they need to be sync'd and the fuel/air mixture screws need to be adjusted (colortuned).

[mxmikie]

carb float level

[ManagerMike]

Simple: too lean at closed and near closed throttle.
Bad news: more than one possible cause.
Pilot circuit(s) restricted or misadjusted, carbs out of sync, one or more floats out of whack. Or of course all of the above, or any combination.

As far as hard on gas goes, these bikes aren't known for geat fuel economy (as bikes go). Properly tuned and adjusted, fuel econ is more wrist factor than anything else.
As an example, my 78 will run like a scalded dog, OR get 40 mpg, but not both at the same time, if you take my meaning.

[CatatonicBug]

As an example, my 78 will run like a scalded dog, OR get 40 mpg, but not both at the same time, if you take my meaning.

Well stated! I like that one.

[natemoen]

These guys got you covered so far. As stated, start off with a GOOD carb cleaning (search for the thread carb cleaning 101 by wildkat).

Some where in the 30s is normal for mpg.

[bikerphil]

Clean, re-check the float levels, and re-sync. Be careful not to strip any pilot jets or break any float posts.

[DGXSER]

As previously stated, sounds like she is running lean at low RPM or in the pilot jet circuit. You can try simply opening the mixture screws a 1/4-1/2 turn, may cure it.

I will say that it is always good to clean the carbs and know their condition. If you do not know the last time they were cleaned, definitely do it this winter. Also check the jets while your in there. Check the number and style of pilot jets. Seen a couple or more sets latley that had the VM style (8 holes) pilots installed instead of the BS30/96 style (6 holes), or even worse the ones in Banshee when I got it were N151 with no holes. JAT.

[81xsproject]

Before you go tearing things apart, it is worth your time to try and run a couple cans (total) of Sea Foam through a few tanks of gas. Sure, it is the lazy way, but I have seen it work if the carbs are just dirty.

[planedick]

First

Synch the carbs and adjust idle screws for smoothist idle and repeat. If that don't do it then take 'em out and clean them and check float height.

[rickybeaver]

Sea Foam

Good advice on the seafoam!! I put one can through and it cleared the popping up some. Seems to do it more once it gets hot. But along with the popping it was running very rough at around 1500 rpm's. Well since I put the seafoam to it, it is very smooth at 1500 rpm's. Might try another can. But I admit it probably still needs a cleaning and possible jetting.Rick

[BigRed]

I hope the sea foam finishes clearing up your problem, but if you do have to take the carbs off, one thing to do before you remove the carbs is check the fuel level in the bowls. You snug a clear tube on the drain, and loop it up above the carb, and open the drain. That's the only accurate way to check the fuel level, and you don't have to take the carbs off the bike to do it. You should do it on all four carbs.

[DGXSER]

Big Red,

That only works on the 81 and later model carbs. The 80 and earlier models only had a drain plug, not the bottom nipple with the side drain plug of the 81 and perhaps XJ carbs.