TOPIC:

Sorry guys I am back again.
After ( as we all know) a long time and lots of advice from other members I finally got the bike running on all six, albeit I kept losing cylinders 2 and 5. At least it was not the carbs they are doing exactly what they are designed for and delivering fuel.
I had to buy a dyna ignition system from a four cylinder bike ( ebay) and replaced a pick up, this was not too difficult and now works fine.
I have only covered 50 odd miles and found that I kept losing 2 and 5 again and that it started smoking. I have carried out a compression test and found that 2 and 5 are down to 90 psi, the others are steady at 110 - 120 psi. What is the correct psi reading for these bikes on std pistons?
Interesting though, when I start the bike from cold 2 and 5 do not get hot, it is only after 5 minutes or so that they cut in and start working, then when it gets hot it smokes a lot.
When I originally stripped the bike the pistons were like new ( previous owner must have cleaned them up ) and the bores had no rust at all, now I had the bike stored for 8 months while I was busy doing other things, could I have stuck rings or possible valve leakage. I looked for the compression test set up but I have failed to find it.

Hello sixpipes,

I have had a similar issue with my bike.
My bike had been sitting for slightly longer than yours though.
When I initially checked the bike over all my valve clearances were spot on, compressions were all about 110 - 120psi.
When I got it running I also had issues with 2 cylinders dropping out, just like yours.
After alot of fiddling I got her running pretty well and took her for a couple of short rides.
My poor old girl started blowing blue and dropped a couple of cylinders.
Did a compression test and I was down to 85 - 90 - 120psi.
Decided to strip her down, in the process I checked my valve clearances again and found that they had tightened up.
I continued with the strip down and found that my bike still had standard pistons to.
When I removed the pistons I found that 4 out of the 6 oil rings had stuck in the grooves, hence my oil burning issues.
My bores all look really clean.
I am now in the process of having the bores checked to see if I go down the hone and new rings track or 1st oversize rebore.
As far as correct compression readings as far as I am concerned anything around 120 and over is good.

some quick thoughts-
You still have ignition problems on 2-5 (same coil for those 2 cylinders). I suspect that since the pipes are not getting hot for the first 5 minutes, that raw gas is washing the cylinder walls, rings and pistons and that's not good. I just bought a cylinder leak down tester from EBay for $39.90 + 15.50 shipping and I wouldn't be without one. It answers all the mechanical questions related to low compression and it quantifies the leak rate as a percentage so you can judge the wear and tear on the motor.

One test you should do before anything else is put a teaspoon of oil down the sparkplug hole and rotate the engine over on the starter for 10-15 seconds, then redo your compression test. That will tell you (if the cylinder walls are washed down) what the compression should be if the cylinder was firing and not allowing the raw gas to wash down the cylinder and associated components. If the compression comes up, then deal with the spark problem.

A cold fuel / air mixture is harder to fire than a hot one which is more homogenized, so a weak spark will not fire a cold cylinder. Another thought is that an oil soaked plug will be basically a dead short and with this dual plug per coil, the spark will always go to the shortest distance to ground which in this case is a dead short. So, a dead short will kill two cylinders. And possibly the raw gas washed off the oil soaked plug and cleared the issue (doubtful but had to throw it out there)

I really like to have two test sparkplugs for checking for good spark. Take a couple of sparkplugs and open up the gap to 3/8" and place them on #2-#5 plug leads and ground the plug out to the cylinder head and see if you get a clean blue spark across that gap. If it produces a spark across the 3/8" gap, then it will spark under compression, if not then you are pointed in the right direction. Also, you could confirm the test by trying the spark setup on #1-#6 and on #3-#4

That's all I have for now. Good luck and keep us in the loop.

Just have to add that actual compression numbers are less important than the compression numbers as compared to each other. If they're a bit low, it's still gernerally okay, so long as they are within 5-10 psi of each other (although 10 psi is pushing it).

Still, it's odd that it would hit on two cylinders at once. 2 and 5 share a coil, so I would definitely start there. Anything deeper means a WHOLE lot of work and expense.... If ignition is your culprit, and you can get them firing reliably, you may see those compression numbers come up.

What color is the smoke that is blows out? White and sweet-smelling, or blue (which would be oil)? Black is, I think, too much fuel.

Its blue smoke and the pistons on 2 and 5 look as it they have oil all over them.

Sounds like a ring problem. Lapped or broken. But twp pots on the same coil? Gotta check that out first.

Bill