[scuba14c]

Alright, it turns out the engine isn't running so well. Cylinders 1 and 3 are running and producing heat. Cylinders 2 and 4 will puff smoke when the starter motor is turning the engine over, but as soon as it catches, it just blows air, not exhaust. One bank runs, the other doesn't. There is also a lot of backfiring out of the non running cylinders, both through the carbs as well as out the exhaust.

Here is the first thread-

Not starting

The engine is from a 1983 VF750F Interceptor

Here is what has been checked-

1) All electrical checks out fine. I get spark on all cylinders, the CDI boxes are identical when tested, as do the coils and spark generator.

2) All cam timing was set to T1-3. I tracked the valve opening and closing and the firing order (1, 4, 3, 2) is correct.

3) I cleaned out the carbs and checked the low speed and main jets as well as their tubes through the carb set.

4) When I spray starter fluid down the carbs for 2 and 4 when 1 and 3 are running, they don't noticeably pick up speed.

5) When 1 and 3 are running, 2 and 4 exhaust air and gas.

6) The valve clearances are .005 inches all around.

7) Compression, the last time I checked, was between 120 psi and 150 psi when cold.

8) The fuel is being gravity fed.

9) The plugs are new.

10) 2 of the carbs are side draft, 2 are downdraft. (don't know if it matters)

11) The timing can be checked, but I don't have the equipment, and it is non adjustable. Any timing problems would be the fault of the CDI boxes (see # 1)

12) There currently is no cooling system in place.

13) It's roughly 50F when trying to start it.

14) The throttle has to be feathered and the choke manipulated to get it to start the two running cylinders.

I am at a loss as to why these two cylinders will not run. I would appreciate any info to fix this.

Edit: Here's a video of it running on roughly 1.5 cylinders in case it helps. You'll need a facebook account to get to it.

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