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[mcdonaldroadcapt]

My son has a 2008 Road King CVO.  It was dynoed using the SE Pro Race tuner by the dealer when new and has run great for two years.  Just recently it has started to backfire back through the air cleaner when cranking if the engine is hot.  Took to dealer today to check to be sure that the ACR's were still set ON and all checked out OK.  They claim it is a starter problem which we just don't buy at 6,000 miles. It cranks cold with no problems every time.  However when hot, the engine acts just like my built to 95 CU IN 10.5 to 1 Springer when I forget to press the manual compression releases.  Any ideas?

Thanks

[kraut]

sorry, no help for you 

But I can tell you the story of my 05 FLHRCI SE 103 (high comp, SE 260 cams, SE manifold and some other mods) . Bike ran great for some 6.000 m, than out of a sudden developed this bad habit too. Had it at 3 separate dealers, the tech district manager inspected it: no clue. Only comment: some high comp. bikes do that  So I tried to avoid restarting the bike when hot.

Over the years, the bike got one fresh engine (06, 20.000 m) and one complete rebuild (08 50.000 m) - almost nothing mechanical left unchanged, heads, manifold, injectors, cams, mapping - but the "spitting" never quit ...

Only positive fact: the engine suffered 3 fatal incidents (the last 09 at 60.000 m) but evidently none of them had anything to do with his "bad habit" 

I traded it in and the dealer did the next rebuilt: miraculously the backfire disappeared 

[mcdonaldroadcapt]

Thanks for the reply.  However, the stock 9.3 to 1 compression on the 110 seems too low to cause the spit back when the ACR's are working.

My old 95 cubic inch is running 10.5 to 1 and will crank fine hot if I can always remember to set manual compression releases. Forget to set them and I get the same problem you mentioned.

[sadunbar]

Thanks for the reply.  However, the stock 9.3 to 1 compression on the 110 seems too low to cause the spit back when the ACR's are working.

My old 95 cubic inch is running 10.5 to 1 and will crank fine hot if I can always remember to set manual compression releases. Forget to set them and I get the same problem you mentioned.

9.3 to 1 compression ratio is relatively low, but the 255 cams develop about 225 lbs of cranking compression, which is very high.

I suspect the root cause of your issue is the stock compensator has lost tension.  I'd recommend upgrading to the SE compensator.  See the attached link...