Hi all,
I have a 1973 cb500 four.
the top end has been rebuilt with a NOS 555cc overbore kit purchased off ebay. The kit came with new 3mm overbore pistons and rings, and a new head gasket. I had a reputable machine shop bore out the stock 500 barrels, as well as go thru the head and replace the valve seals and guides (I asked them to do whatever it needed, they even replaced all the tappet adjuster screws)
A friend and I did the assembly at our shop. We followed the clymer manual step by step, and torqued everything to spec.
All gaskets and o-rings were replaced.
The bike has a brand new MAC performance 4-1 exhaust, and the carbs are fitted with UNI foam filter pods (model PK-23).
As we were aware this would put the engine in a lean condition, I had a custom jetting kit designed by 6 Sigma Engineering. They design the jetting specs based on the bike's mods, and operating altitude. It has 120 main jets, and the needles have been moved up to the next position (right now they are at the 2nd to last position, one more and they will be as high as they can go)
New oil (20w50) and filter, new plugs, new coils, wires and plug ends.
We got the bike running with the header pipe on at first (no muffler).
It seems to idle really nice, with only a bit of popping (likely points are getting a bit worn, but they were filed and gapped - I have a set of dynas on order, but wanted to see if the bike would run as is for now)
The throttle seems to have lots of snap and is very responsive, (didn't ride it tho, clutch cable and brakes were not hooked up)
Here is the main problem
It immediately began to emit a lot of white smoke from the output of the header (not vapor, as it hangs in the air and does not dissipate easily). Revving it only made it smoke more
We also noticed a bit of an exhaust leak from the number 3 exhaust where it joins the head. The crush gaskets were new, but we may have overtorqued that one.
We ran it for about 2-3 minutes, then let it cool down. On the second try it started first kick, and we ran it some more to see if the smoke would burn off (we figured it might just be residual oil from oiling the cylinders during assembly?)
this time we let it run for about 5 minutes, but the smoke still did not go away. On the third try we put the muffler pipe on. It was then I noticed a tiny bit of oil? (or dampness) on the bottom of the collector where the muffler joins the header. No real change, it still idled nice and sounded good (no tappet rattle, they had been adjusted prior to startup). We let it run, revving it occasionally, but the smoke kept spewing out the exhaust. We noticed what looked like oil had collected in a puddle (about 5 inches across) under the collector part of the header, but in retrospect it may have been water mixed with carbon? (it sure was black...) I'm pretty sure it was oil though, it felt oily on my fingers
We pulled the plugs and they seemed black and wet.
It seems to run soooooo good, if it werent for the smoke. I would think if it were bad rings, it would not run at all? And as I said, the rings are new, as is the head.
What could be wrong? Could they have forgot to do something in the head?
I've tried to detail as much as possible everything I can recall for some of you more experienced folks to narrow it down, but may have forgot something. Where should we start at this point?
Any help?
Jacob
