Engine races after rebuild...any ideas?

[Naturil]

Hey guys,

little back story:

I just rebuilt the top end on my '79:
Honed cylinders, new rings, new tensioner, new front guide, new valve seals, lapped valves. New advance springs (bike has pamco).

I got everything back together yesteray and it started right up so i timed it and synced the carbs.

Problem is when you give it any gas it races to approx 3k rpm and will just stay there. But if you let the clutch out (put in gear) you can get it to go back down to normal idle. The carbs on the bike are fully rebuilt bs34s (rebuilt 600 miles before top end was rebuilt) and it never used to do this.

Any ideas,

Thanks.

 

[5twins]

If the new advance springs are from Mike's, sometimes they're no good, weaker than what was in there. Many just shorten one of the originals by one loop (only do one spring and test, do the other if need be).

 

[Naturil]

Thanks 5Twins,

I put the old advance springs back in and it fixed the problem...sucks when you put "new" parts in and they cause a problem.

 

[retiredgentleman]

As is well known by many of the experienced riders here, many parts from Mikesxs just plain don't work.

I tried their advancer springs, and just could not get them to work properly. I went back to my stock OEM springs and they work great. Rule #1 with these bikes.............never throw out OEM parts.

Ask a few questions here on the forum before you buy parts from Mikesxs.

Air inleakage around the carbs/manifolds/throttle shafts will also cause the idle to hang, on the high side.