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**Pat Kelly** · 09-13-2008, 04:10 PM

Make sure the petcock to 3-4 has vacuum (BTDT). Make sure that (with vacuum) there is fuel flowing to these two carbs (does fuel flow out the bowl drains?).
Then check that the intake and/or exhaust valves are working/sealing properly.
Is there spark to those 2 cylinders? I know the coils fire 1-4 and 2-3 but it is possible for those two particular plugs or wires to be not working as they should.

**AlanB** · 09-13-2008, 04:16 PM

Hi Chuckster,

You are probably right to be chasing fuel problems; have you checked to see if you have a good supply from the right-side petcock?..... Have you tried draining the bowls and checking to see that they refill when the fuel is switched back on?

When you cleaned the carbs did you check the little filters above the float valves?... did you clean the passages to the enrichener jet on the base of the float bowl?....

Lots more questions to ask; those are just a few to start with!

AlanB

**Chuckster** · 09-13-2008, 04:21 PM

The carb bowls both have fuel in them. I tried both my fuel tank and an auxiliary tank where no vacuum needed, so I know fuel is flowing. Also, I swapped wires and plugs and they fired fine in 1 & 2.

I don't have a compression gauge, but I know 3 & 4 fired before. I did the thumb over the spark plug hole test and there seemed to be compression. Should I buy a gauge and test?

**prometheus578** · 09-13-2008, 06:20 PM

Time to start over.

"I checked this and it's good, I checked that and it's good, etc......"

Simple logic says that something isn't good, so we start from the beginning again.

Ok, #3 and #4 barely warm.
Warm means they are getting spark, and as you infer that the sparkin' system is good, we shall pass over this area.

I know you mentioned new plugs. What do they look like now?
If they're sooty and carboned fouled, throw them out.
If #3 and #4 look good, but appear wet after trying to start, then you have too much fuel, or an inconsistant spark issue.

Common things that are forgotten when cleaning carbs... cleaning the little jet, in that tunnel, in the float bowl. This supplies fuel during choke. If that's plugged, no fuel for choke, cylinders don't fire, and the bike never get's warm enough to run off choke.
Not running at idle means the pilot circuit. You should be able to squirt carb cleaner in the air jet(air filter side o' the carb, and have it spray out the tunnel holding the pilot jet. In carbs of your year, the pilot jet tower is plugged by a screw.
Placing a finger over the tower and spraying again, carb cleaner should come out the hole that the pilot screw meters, and also the small transitional holes by the throttle plate.
Re check that the tips haven't broken offa the pilot screws and plugged the hole in the carb throat. Your bike is exhibiting symptoms of that.
That should take care of the carb issue.

compression. If you have poor compression on #3 and #4 cylinders, I mean really poor, you won't get the vacuum needed to lift fuel from the bowl.
When was the last time you check valve clearances? Clearances lessen over time. If you have a clearance that is now wider, you may have a bent valve. (loss of compression and fuel-suckin' vacuum)

I don't have a compression gauge, but I know 3 & 4 fired before

I've had a bent valve... clearance was like .035in. Bike was hard to start, but would run eventually... and at higher RPMs would suck fuel into the bad cylinder and even out a bit.
Pick up a compression gauge from Sears and check. Always good to have tool.
Another possability.. vacuum leak at the carb or manifold boots. Loss of vacuum... less fuel being sucked up from bowl. Those nipple caps(Woo Woo!) where you hook up the synch gauge can harden and leak vacuum.

Have you had this bike running well before?

**Chuckster** · 09-13-2008, 07:22 PM

I should probably make it clear that the bike hasn't been running in over 10 years. It's been garaged, but hadn't run. Total running time since April is only about a half hour? pretty much while trying to synch and adjust. Without brakes being done, I really couldn't take it out and run it. That's why it's hard to tell looking at the plugs, they all look pretty new (because they are), not much on them to read. I swapped the ones from 3 and 4 to 1 and 2 and nothing seemed different.

I think I've cleaned the carbs pretty well. In four tries, I can't believe I've missed anything, but if I have to I'll give it another shot. I pulled the pilot screws and checked them all, all are intact, no broken tips. I watched carb cleaner come out of the small holes, this can't be the problem.

I noticed when I rev it up numbers 3 and 4 start to get hot. But when back to idle they cool down.

I will get a compression gauge and check compression tomorrow.
I thought I would get it running right and then check valve clearance, but maybe now would be a better time?

**Chuckster** · 09-13-2008, 07:30 PM

I noticed on my last trip thru the carbs and rechecking the heights on the floats that two were off. I reset them again. Should I try changing the heights on 3 and 4? Could this be the problem?

**TopCatGr58** · 09-13-2008, 07:51 PM

Hey Chuckster,

HOW did you clean the carbs......like did you soak the bodies in carb cleaner??

IF SO...then you may have damaged your butterfly shaft seals and getting severe vacuum leaks!? IT runs at higher rpms, and the the 3-4 pipes start to warm up, so you're getting fuel and spark at higher rpms, but not at the lower rpms. At low rpms, IF there is a vacuum leak, the pumping/sucking action of the engine won't work as well, and so won't draw fuel thru the pilot circuit effectively, but with higher rpms, the pump is working faster, and can then draw enough fuel to feed the engine!

As Prom eluded to, the synch ports are one possible vac. leak source, also hoses to petcocks could get cracks and leak. Also the intake boots....where they fit against the head, rubber can get hardened, crack, etc. as well as the boots themselves crack and leak, although they are double walled, and rarely develop leaks thru to the inner layer!?

Check for vacuum leaks!
T.C.

**prometheus578** · 09-14-2008, 12:54 AM

I think I've cleaned the carbs pretty well. In four tries, I can't believe I've missed anything... ...I noticed on my last trip thru the carbs and rechecking the heights on the floats that two were off

Uhmm... does this mean that on time 1, 2 and time 3 you didn't "clean the carbs pretty well"?
Like I always say... everyone overlooks something, sometimes.
Float levels should be the same for all carbs.
I'll also bet that... with all the attempts to synch a barely running engine, the synch is pretty goofy right about now.
I'd pull the carbs and verify the best that I could that I have an accurate "pre-synch"
The throttle plates on #3 and #4 could be all the way closed, hence no fuel. (all throttle plates need to be open just a little bit to even start.)

**Ken Talbot** · 09-14-2008, 08:47 AM

Originally posted by Chuckster
I noticed when I rev it up numbers 3 and 4 start to get hot. But when back to idle they cool down.

And there's the answer. The low-speed circuits on #3 and #4 are dirty. Plain and simple. Sorry

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