Intake boots

[Suzukian]

My '83 GS750ES is so cold blooded, when I purchased it, they told me to get used to running it with the choke on a long time. They weren't kidding. I lifted the needles one notch, and that gave me a lot more midrange, but it's still a cold blooded animal. Once very hot, it's no longer an issue. I think it's normal for bikes of that era.

 

[Robyle3]

That’s reassuring haha. Honestly one of the things I love about old bikes is how they have characters like this. Needs just as much go-juice as I do in the morning haha

 

[Suzukian]

It's good to know. That way you don't go chasing something that isn't broken.

 

[rphillips]

Lots of us local folks went up one size, from stock, on the pilots, to help the cold starts. Some say it won't help, but for us it seemed to make it noticeably better. I've raised the needles on a few, but mine never had notches, had to put shims under them, that was for mid range, I don't remember it changing the cold starting.

 

[Suzukian]

If it's really cold, I just pop off the seat, and the bike will start very quickly with a hand over the intake, once running, you can even rev and do that till the bike gets warm, and need no hand, seat popped back on, and I'm on my way. The needles worked shimmed worked for mid range, but these are cold blooded beasts.

 

[Robyle3]

If it's really cold, I just pop off the seat, and the bike will start very quickly with a hand over the intake, once running, you can even rev and do that till the bike gets warm, and need no hand, seat popped back on, and I'm on my way. The needles worked shimmed worked for mid range, but these are cold blooded beasts.

Good thing the seat is soo darn easy to get off!

 

[Robyle3]

If I’m chasing air leaks, am I mainly looking on the intake or engine side of the carbs? I just had a thought that the intake will only intake soo much, but the engine side and the intake manifold boots are where extra air would come from. Am I thinking about this too much or am I on to something?
Appreciate all the help soo far from you guys here! Bike is parked while I get the starter rebuilt, so have time to do more research.

 

[KiwiAlfa156]

Engine side is the high vacuum/fuel-air mix side. So air leaks here upset all the good work your carbies have done. Air leaks upstream of the fuel metering is comparatively low vacuum so a small leak here is unlikely to affect carburation.
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[Robyle3]

Hate to leave anyone hanging on this, but I found a temporary solution! I was going to push the carbs back just enough to take the intakes off to soak them, when I noticed they were still supple and the carbs slid out very easy. Taking a can of silicone protectant (has chemicals known to slightly swell rubber), I DOUSED the boots in spray and tightened the clamps until my screwdriver almost started to slip. Ideally I’d let it soak into the rubber over the afternoon but out of curiosity I tried to start it.

Needed full choke but it idled perfectly at 1500rpm, and once it warmed up it bounced up to 2500-3000rpm after a minute or so. Dropped the choke and blipped the throttle and it settled around 900-1000rpm. Idle also doesn’t hang NEARLY as long as before. I’ll adjust the idle screw after work but it turns out that tightening the boot clamp was all that was needed in my case! At least now I have the solution required to refurbish any other rubber parts around the house haha.

 

[Robyle3]

Turns out I was too optimistic this afternoon haha. Took it out for a short run and it was still shooting up to 3000. Though now that I know the rubbers still have some life in them I am turning my eyes toward the carbs. I made an attempt to take the boots off after work and the starter plungers were filthy and coated in gunk.

 

[Suzukian]

Getting closer to the problem. Do a complete cleaning of the carbs.

 

[Robyle3]

So I pulled the bike out for the first ride of the season, and promptly flooded cylinders 1 and 2 lol. I took the carbs off over the winter and they are as clean as clean can get so clogged jets are not the issue at all. I replaced all the plugs too, because I got too excited and snapped one because I forgot to take the boot off lol. Some proper NGK D8EAs haha. I’ll see if I can find the thread again, but after my first ride of the season the thought hit me: I’m having issues starting the bike without the petcock on prime, I idle high after a few minutes, and when I pulled my plugs all of them had white tips on the ends….i think I need to up my jets! Too much air makes it run hot, and even if the jets are perfectly clean, if they’re not big enough there will always be too much air in the piston. The previous owner put a 4-to-1 exhaust on it and I’m thinking it’s just running through too much air. Can’t remember if I listed the jets here but I’m thinking I should just got up a size to see if that makes the problem any better.