Rookie Mistake - Chem Soaked Butterfly Valves

[curtis]

So I screwed up. Am working working on a '79 XS11 with similar carbs to my '74 XS650.

This weekend I pulled the carbs, disassembled and chem dipped them. I checked the parts book to make sure I'd gotten anything rubber or plastic out, but my book didn't show that there are rubber seals around the butterfly valves. So I soaked the whole dang thing.

So how can I tell if my butterfly seals are wrecked? After reassembly, bike started up (bit cold blooded) and would idle fine. What should I be looking for if the seals are now bad?

Thanks in advance.

 

[TeeCat]

I'm no carb expert, but if the butterfly shaft seals in one or both carbs are bad, you'd likely have an air leak that would, at the very least, make it a challenge for you to sync the carbs. These bikes are cold blooded by default, so if I were you, I'd watch for a wonky idle or a flat spot, but in the absence of that, I'd assume that the seals are unscathed... this time.

TC

 

[curtis]

Thanks TC. Not sure if I'm going to attempt the sync myself or get some help on that idle or flat spot should be easy enough to check for...

 

[TeeCat]

curtis, if there's a flat spot (in this case it would be the result of an air leak/lean condition), you'll feel it. It could be just off-idle, or elsewhere. But you'll know. If it's not there, I would not worry about it for now... your seals may be fine.

As to the carb sync, there is a good discussion in Tech (links up top) about the "dead cylinder" and other methods.

TC

 

[MAndrade1980]

(Newb Question) what did you use to soak the carbs? just a traditional carb cleaner, anything special?

 

[littlebill31]

I would replace the seals anyway. They get hard and don't work. Cheap fix now, or have to disassemble them again later.

 

[gggGary]

The normal "seal test" is spray carb cleaner on the shafts with the engine idling. An increase in idle speed = seal leaks. Not addressed with this test is the effect of the carb cleaner on otherwise good seals! As much of a pain as it is to replace seals it's the right thing to do.

 

[grizld1]

If the seals are good, carb cleaner won't get sucked into them and will do no harm--you don't soak the area when testing, just fire a short burst. Also, idle speed may increase in response to spray. It may also drop. Wait a couple of seconds for response. But TC's advice is spot on--don't troubleshoot if you have no trouble. You may have been lucky. Yamaha's carb cleaner is rubber friendly, and if that's what you used, your seals will be no worse for the dip.

Don't change out the seals just for grins. If you find that only outer seals are leaking, change those and leave the inner seals alone; removing and reinstalling the throttle plates is touchy work, and there are plenty of 30 and 40 year old seals still doing the job.