The bike went BANG on start up

[Motor31]

I had an interesting day yesterday. I had been running errands on the bike and it was running just fine.

After picking up a package at the pharmacy I hit the starter. The bike had an immediate LOUD backfire and started to run like an old beat up gas lawn mower. There was no smoke or oil spewing so I knew it hadn't thrown a rod or perforated a piston.

The running sound was pretty loud too so I thought at first it blew out an exhaust gasket at the cylinder head or some place at the pipe. Then I realized it was running really rough on one cylinder only including at rev up. I managed to limp the mile and half back to the base (DM AFB) and called the mechanic. He asked me to check the positioning of the right throttle body but it was right where it was supposed to be, with the adjusting screw in the access tear drop hole. He was getting ready to go to run a tour into Mexico this weekend and couldn't take it in the shop but would stop by on his way home to look it over. :scratch

I pulled all the tupperware off (1150RT) and saw the problem. The right throttle body had been blown off of the cylinder. It took a hell of a lot longer to get the tupperware off than it did to fix the problem. I put the throttle body back into position and the bike fired up normally and runs fine again. :dance

I figured I'd post this little experience in case other folks might have the same issue. If I had a "naked" bike it would be obvious right off the bat. For the RT's the plastic covers so much that you can't see diddly other than the valve covers and exhaust manifold.

[henzilla]

Wow!, that ended a lot better than it originally sounded. So it just blew out of the collar a little? the tube to the airbox just held it there?

Glad it ended well, that's a first I ever heard of that happening.Now if it had been parked and the mice had filled the exhaust....:whistle

BTW...for the non military...where is DM?

[2BikeMike]

Davis- Monthan Air Force Base, AZ

[cruisin]

When I saw the title to your thread I was going to say look at the intakes to the cylindars and see if one has blown off. I only knew that because several folks on Chromeheads have reported the same thing happening with R1200Cs... this is the first time I've hear of it happening to an 1150RT though. Glad you found and fixed the problem easily.

[kgadley01]

I'm so glad you posted this. If I ever hear a loud bang on my RT, I'll know where to look. Why do you think it blew off?

[JimMoore]

The loud bang has happened to me about a half-dozen times in 98K miles on my GS, always on a hot start. I've never had the throttle body blow off though. Traumatic, but harmless.

[Motor31]

DM is in Tucson AZ.

The only thing I can think of is that there was a charge in the manifold when I started to crank the engine and it backfired. With the butterfly closed it pushed the throttle body off of the cylinder. It was almost instantaneous with hitting the starter button. I don't know if both sets of plugs fire simultaneously or if they are staggered with the crank rotation to only fire after compression. If they fire both sides together it could create the backfire if there is fuel / air in the off side manifold The mixture would touch off as the exhaust side would have the valves open and the plug firing with the compression side.

I figured to post this as I hadn't seen anything like it on the board before and others might just get the same situation. It really does get your attention.

[osbornk]

The same thing happened to me at the RA rally at the Biltmore. I immediately pictured a major problem. Fortunately, my riding buddy had experienced it before on his GS and I was back up and running in about 10 or 15 minutes. It apparently can happen to any oilhead.

[bobs98]

It pays to check those clamps and keep 'em tight.