Overflow into Cylinders

[Senator_Kang]

Hiya guys and gals!

I have 2 issues:

After cleaning my carbs I primed them and petrol ran out of one fuel overflow. Took another look and the needle valve on #3 carb is buggered. I notice that the overflow appears to be linked for #3 & #4 - one overflow for 2 carbs (if I'm looking at the right hose...). When I take the carbs off, there is fuel pooled/wetting the intakes of cylinders 3 & 4, but not on 1 & 2.

- Am I right in assuming that's because of the screwed needle/seat and that both are being flooded because the overflow links the two carbs together, and hence 2 cylinders together?

Second issue: I pulled the plugs for a different reason and number 2 is clean as, 1 3 and 4 are wet with fuel (I had been trying to start it for ages at this point). I noticed one of the diaphragms had a wear mark, but it didn't appear to go all the way through. If that diaphragm was screwed, would it stop the fuel entering at idle/start up speeds? Or am I looking at another blockage here?

Thanks!

[Fj.itis]

To answer your question, yes one carb will leak into another and make it overflow as well.

To help you save yourself some time, do each carb individually and get everything spot on and check for leaks. That means float heights, needles and seats making sure its shutting off fuel ( take off fuel bowl and rest the float on some sponge to close it off and fill from inlet hose until full) this way you can check where the leak is coming from, either needle or seat outside o'ring. If it doesn't leak when set up like this but does in normal function then float is to high.

I doubt the diaphragms have anything to do with this especially since they have no visible holes.

You need to be methodical about this and be 100% certain all aspects of the carb are perfect.

So check all holes are clear and floats move freely
Check if any leaks like i described with one float bowl off at a time
Check float heights
Sometimes the seats have a flat spot where people have removed them with pliers a bit to forcefully and that makes the needle stick and not close completely, so check that as well.

Hope this helps

[giantkiller]

Also check your oil. I had my crankcase fill with gas twice. Once before I put the manual petcock on the 86. And once after, when I forgot to shut it off.

[Senator_Kang]

Thanks! Yeah I'll take em apart again. At those engine speeds/throttle openings it'd be a pilot jet issue, right?

Yeah I figured I will just change all the oil and grab one of those spin on oil filter adapters from RPM when I get the other bits and pieces. I should add that it is no longer leaking out of the overflow pipe when it's on prime, so either the needle valve decided to close or it's dumping ALL OF IT into the cylinders and somehow not out of the overflow, so yeah, I'll change it 

If it doesn't leak when set up like this but does in normal function then float is to high.

Well, the needle bit isn't springy anymore like all the others. I would have thought that'd make it close too early rather than stay open since the springyness appears to push the float away from the rest of the carb (i.e. down when it's all assembled), so it'd rise up and close it too soon. But if it's broken it's broken, I'll just pick up a whole new dealy.

I doubt the diaphragms have anything to do with this especially since they have no visible holes.

Yeah, I was a bit unsure. I didn't think the wear mark would impact it much. You can just see the cloth part where the rubber has worn away but only from one side and only a few mm in length. I know carbs are supposed to be sensitive but I'm not sure if they're THAT sensitive.

[Fj.itis]

It wont be dumping fuel into cylinders without visable overflow, well thats what i would of thought anyway.

If it did leak before, you might be lucky but my experience is that there is always a reason why they leak in the first place. You need to make sure there is not a reason, otherwise it will do it again and you will be removing the carbs again to find problem.

Check the needle falls in and out of the seat with the seat and needle removed from carbs. Just tip it on a 45 degree angle and the needle should fall out with ease, also check the roundness of it. If thats ok sometimes the oring can develop intermitent leaks on the outside of the seat ( happened to me), sometimes it would leak and other times it wouldnt. I replaced it and havent got a problem since.