goatman123 Posted August 1, 2011 Share #1 Posted August 1, 2011 Well I got my 93 up running with a carb rebuild, but I noticed the revs slow to come back down, so I figure a vacuum leak. I sprayed carb cleaner around the boots that attach to the head, and sure enough the revs jump up on all four cylinders. I see there is an o-ring in the boot assembly. My question is, can you usually get by with just an o-ring change, or do the boots themselves routinely go bad? The bike has less than 19,000 miles on it, so it has spent lots of time sitting. Thanks. Link to comment Share on other sites More sharing options...
Squidley Posted August 1, 2011 Share #2 Posted August 1, 2011 If you talking about the Oring that is between the intake manifold and the head you could do that, although I haven't run into a failure there. The cracking on the actualy intake boots looks ugly but many times do not go all the way through to cause a vacuum leak. Something I will mention is that make sure that all your carbs are completely seated all the way on all the intake manifolds, it's easy to not get them all the way on. Another tip is do a carb sync as many time if it's off it will be slow to come down to an idle...just some babbling on my part Link to comment Share on other sites More sharing options...
goatman123 Posted August 1, 2011 Author Share #3 Posted August 1, 2011 Thanks for reply, I can tell when I spray carb cleaner that the vacuum leak is where the carb boot meets the engine. The boots themselves look good, no cracking that I can see. I haven't gotten as far as a carb sync yet, because of this vacuum issue, but I'm sure it will need it. Link to comment Share on other sites More sharing options...
KarlS Posted August 1, 2011 Share #4 Posted August 1, 2011 My 83 did that until Squidley did a carb sync when he was still a Michigander. Link to comment Share on other sites More sharing options...
MasterGuns Posted August 1, 2011 Share #5 Posted August 1, 2011 Had the same problem with my former 86 motor. After I learned the PO had the carbs off more than a few times, I went through the same process as you; spraying ether and wd 40 around the maniford boots. I had one boot that increased the rpms significantly. Tore it apart and turned out my problem was a stripped maniford/boot bolt. I used a longer bolt and that seemed to eliminate my problem for a while. I ended up replacing the entire motor for that reason and one other. The motor after a long hard run of over 1500 miles, developed a knock which I think was a wrist pin. But with the new motor (89) all is well, no stripped bolt holes and no more knocking. Good luck. Link to comment Share on other sites More sharing options...
dingy Posted August 1, 2011 Share #6 Posted August 1, 2011 The intake o-rings are 45mm x 2mm Maybe you can find them locally. One of my motors had permatex along with the o-ring and it seemed to work, not recommending it, just mentioning. Do what you will with this nugget of info. You won't find it in the owners manual. Gary Link to comment Share on other sites More sharing options...
mbrood Posted August 1, 2011 Share #7 Posted August 1, 2011 The lower half of the lower manifolds have a steel insert (to mount with) so cracks down there are really just cosmetic. You can use a scrap of paper to block the spray so you can get a better handle on WHERE it's leaking. I used a Yamabond 4 on my o-rings just as a precaution. Yeah, you gotta pay attention where the long bolts and short bolts go... Link to comment Share on other sites More sharing options...
goatman123 Posted August 1, 2011 Author Share #8 Posted August 1, 2011 dingy, Thanks for that o-ring size. Now I don't have to buy them at the dealer. Link to comment Share on other sites More sharing options...
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