1971 ST90 Leaking Gasoline, HELP!

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BlackMamba

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I have been having trouble with my 72 ST90 since I bought it. Took it to two shops with the complaint that it wont start, and a possible gas leak. The first shop gave it a once over and said it was just out of gas, I explained I filled the tank up a few days previously and there was no way it could be empty. Sure enough it started up and I rode it home. It was stills very hard to start up and took push starting and a lot of kicking to start up and a few days after riding to work, the leaking started again. I took it to a different mechanic and he did a routine maintenance job. Took him a bunch of times to get it to kick start and work, again I rode it home and a few days later of riding it was REALLY leaking (both when ridden and turned off for days). It is no longer leaking since I haven't ridden it for months. I am very frustrated at this point and really unsure of what to do or what it could be.

So, leaking gasoline from the drain valve of the petcock as well as taking a LOT of kicks to start my bike when I was riding. Anyone have any ideas? Know anyone in the Kansas/Missouri area for a good older bike mechanic?
 

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BlackMamba said:
I have been having trouble with my 72 ST90 since I bought it. Took it to two shops with the complaint that it wont start, and a possible gas leak. The first shop gave it a once over and said it was just out of gas, I explained I filled the tank up a few days previously and there was no way it could be empty. Sure enough it started up and I rode it home. It was stills very hard to start up and took push starting and a lot of kicking to start up and a few days after riding to work, the leaking started again. I took it to a different mechanic and he did a routine maintenance job. Took him a bunch of times to get it to kick start and work, again I rode it home and a few days later of riding it was REALLY leaking (both when ridden and turned off for days). It is no longer leaking since I haven't ridden it for months. I am very frustrated at this point and really unsure of what to do or what it could be.

So, leaking gasoline from the drain valve of the petcock as well as taking a LOT of kicks to start my bike when I was riding. Anyone have any ideas? Know anyone in the Kansas/Missouri area for a good older bike mechanic?
Click to expand...

That's sad.

Has anyone put a carb kit into it yet? $35 would easily cover the cost of a set of gaskets and a new needle / seat, maybe an hour or two of labour for a carefully done restoration and thorough cleaning.
 
Twenty nine bucks shipped will get you a PZ19 carb from Web LLC. I just put one on my 75 ST90. It has minor issues for fitting but it runs well once you work through those.

But please do not buy any PZ19 without some discussion here. You need the kind with the choke lever on the left and with the two pipe fuel inlet. After that, we need to modify the choke arm slightly to get it to move without hitting the base of the ST90 air cleaner.

And do not throw away the throttle cable elbow from your stock Keihin carb. The new elbow hits the frame and you will need to use your old one.

And finally, the new PZ19 is shorter front to back and has a slightly wider mouth than the old carb. This will require a bit of "reaching" with the air cleaner bellows and stretching at the mouth. But it's all workable.

Yes, you also give up the altitude compensating feature of the old Keihin but that is no factor here in Louisiana. I need more of a snorkel here than anything for mountain air.

Rick
 
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I've had the same problem with both my ST90's. If your handy you can likely fix it yourself. One bike had a leaky float ( if float sloches u need new one ). The other had a bad needle/ seat combo, easy to fix if you look at Honda schematics from parts list.
BTW it's rewarding fixing something that a Honda mechanic overlooked, and it's cheap.
 
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