Bimota Forum

[Locky44]

Hi - I am a new member.
I have a 1991 YB10 that recently developed a starting problem. The engine fires up okay on full choke but any attempt to reduce the choke or touch the throttle results in the engine cutting out. I have removed the Mikunis but haven't pulled them apart yet.
My second issue concerns the reserve fuel solenoid. When I removed the fuel tank one wire was broken & detached & the other just hanging on a few strands of wire. Does anyone know where I can source a replacement solenoid please?

[Jonny B Bad]

The starting problem is likely down to ethanol in your fuel, that has absorbed moisture, which has separated out at the bottom of your tank. So your float bowls are being replenished with water. If you empty the float bowls and the tank and re-fill with fresh E5 super unleaded and add an ethanol inhibitor you should be alright. I had this problem, even using E5, and got quite good at riding the bike purely on the choke, i.e. don’t touch the throttle, for a mile or two, until the float bowls have replenished with fuel, as the water at the bottom of the tank gets re-mixed with the fuel as you ride.

The problem with your solenoid petcock is less easy to solve. These have been in vanishingly short supply for years and they were changing hands for £300 + years ago. You can’t get them apart to repair them, as they are (or were!) a cheap & cheerful item. Probably best to go to a manual version and keep it turned on - no more reserve, but at least you’ll be able to get at the fuel that should have provided the reserve.

Good luck!
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What, Jonny's gone!

[Locky44]

Good advice thank you. I had been using Shell V-Max thinking this would avoid any E10 problems, but seemingly not.
In regard to the reserve switch I guess i'll just have to watch the fuel level. I subsequently read a post that advised a refill every 100 miles or so.

[Jonny B Bad]

While you’ve got the carbs off, there are a number of things that will have it running better and give you a better range. If you want to have a chat about it, let me know & I’ll pm you my number.

All the best
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What, Jonny's gone!

[Locky44]

Thank you. When I came to remove the carbs, all the manifold clips were at different orientations & I puzzled for a while as to how I could get a long-reach screwdriver to them. I gave up but then realised none of the eight clips had been tightened & it was possible to pull them straight off the inlet manifold stubs. Certainly could have led to a weak mixture etc. Different mix of phillips (JIS?) & allen screws too. In ordering a new set of matching screws I managed to loose one clip whilst measuring the thread pitch Certain it will materialise once I order a replacement Anyway I'm going to clean & reset the jets & see how things go. If I can take you up on your offer later that would be great thanks

[Jonny B Bad]

Best bet with the manifold rubber clip screws is to swap them out for M4 socket cap Allen, and use a couple of flexible shafts and a 2.5mm Allen bit.

Good luck
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What, Jonny's gone!

[Jonny B Bad]

Best bet with the manifold rubber clip screws is to swap them out for M4 socket cap Allen, and use a couple of flexible shafts and a 2.5mm Allen bit.

Good luck
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What, Jonny's gone!

[brian]

The running issues that you describe are symptoms of a blocked pilot jet or blockage in the pilot circuit somewhere. Strip the carbs and ultrasonic clean them
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'99 DB4 #104, '96 SB6 #1165, '94 DB2 J #652, '99 DB4 #088, '08 VTX1800, '93 ZXR750R M1, '95 ZXR750, '95 ZXR750 Race Bike, '94 CBR400rr NC29 Race Bike, '94 CB250, '49 BSA C10 250, '61 BSA A10 650, '89 ZXR750, '91 Ducati 851

[Locky44]

Many thanks for the advice Brian