Mikuni carbs on '81 gs750ex

[Makabro]

So i'm cleaning the carbs and replacing the gaskets for the bowls.
rejetted using a dynojet kit.. all went well.

however after testing, carb bowl#2 is leaking just a little.

the screw also didn't fit in very tight, it is easy to remove by hand unlike the others when tightened.

the threads seem to have been fixed by a previous owner like a lot of other things they were not done right.

here is a picture of the threads and also the screws used in carbs 2-4 have these 2 gaps, and the threads are narrower than they are on carb 1.

i'm thinking of maybe just using a bigger gasket? of those little rubber gaskets?

also i'm not sure if these drain screws should have a rubber and a metal gasket or just the rubber, please check out the pics and let me know what you would do as best coarse of action is to correct the slow leak.

I called the suzuki dealer and they said they had the original replacement gaskets for $5 each (which i'm not missing, but it still leaks on that bowl - maybe it's just too old?)

i'm just concerned of the threads being an issue, or maybe i should fabricate my own rubber gasket for these bowls? out of something that wont get eaten by gasoline?

Thanks!

[Makabro]

here is a picture of carb #1 not leaking and threads look to have been repaired at some point and works great.



Here is the picture of Carb bowl #2 which leaks, carbs 3 and 4 look the same and do not leak.

[Guest]

Somebody's stripped out the threads. The #1 picture looks like they put a helicoil or something in there, what ever it is it works. Those little groves you see are supposed to be there, not sure what they do but it's how it came from the factory. The screws themselves would come with either a rubber gasket like you see or a compression washer. doesn't matter what is used as long as it seals. You could try your idea of finding another washer, or the right size o-ring would probably work. Try Canadian tire, they usually have bins where you can buy individual o-rings. They're not Vitron or anything but it's just the float bowl gasket and it doesn't hurt to try. The thread is probably shot or close to it so be careful tightening it. You could also put some gas safe sealer on the thread (Cantire has it, grey stuff) put it in, leave it over night and see what happens. You could tap out the thread, or find another float bowl from someone on here. This will be one of the easier fixes for you I'm sure. Nice bike by the way and glad to see another Canuk on here. Is it snowing in Calgary yet??

[XXWoodmanXX]

It takes an 8mm x 1.0mm pitch bolt in the drain plug, which are surprisingly hard to find replacements for, to my dismay. It's quite possible someone has tried to put an 8mm x 1.25mm pitch(very easy to find) in it's place, and rethread/strip the alum out of the bowel itself.

I tried to get sexy with my own carbs, going all socket hex head bolts throughout, but it looks like I'll be keeping the drain plugs stock.......for now. heh ;o)

[Makabro]

Thanks guys, i'll definitely try the Canadian tire stuff today..
i'll be looking for the o rings and the gas safe sealer, might as well..

I contacted TJ cycles, they've got a large inventory of these bikes, and apparently if i find the right bowl on their yard they'll give it to me for $10, might be worth a shot? for getting good threads?

and yep! it's snowed twice already, but luckily it's long melted by now and people still ride from like 10am - 6pm, outside of that time frame the weather can be anything from -3 to +4 degrees, which is a bit cold for most ppl..

i'll take pics of what happens i'm also considering to buy colortune for tuning these carbs once they got all the pieces together.

[Guest]

Excellent choice with the colourtune, although some people don't have a use for them and just do it by the fastest idle method. I'm guessing you already have a Morgan carbtune?

[koolaid_kid]

Actually, the Colortune is great for VM carbs, not so much with the CV carbs, which is what your 750 has. You would be much better served with the CarbTune.

[Makabro]

Hmm, I thought I would need both, carbtune to sync vacuum and colortune for mixture. I was just thinking of making my own manometer instead of buying the carbtune. Or just visually doing the vacuum sync to carb #3.
Haven't bought it yet though still thinking about it...

I may have found some o rings at auto value. They gave them to me for free unless I need more than 5.. Lol

I'll test that and see how it goes, also I found a gas liquid safe gasket/sealer. It's a tube for $8.. I'll buy it worst case scenario. But mean while I did order a new set of o rings for the carbs, they dont leak anywhere else that I know of.. but I figure its just a matter of time before they do, or I just ride it enough to find out..

I'll test it and get back to you guys.
Thanks for all the replies