200x red hot exhaust pipe

[hogmuffin]

Test running tonight after i Just rebuilt the top end. The exhaust pipe at the head was glowing red hot after 5 mins. It's idling very erratic, rpms will surge up and down. during the rebuild i put a new cam chain sprocket on the crank. looked like it was just a hare off center from the keyway, but pretty close. Found another post on here saying that A lean fuel mixture could also cause this. How exact Does that sprocket have to be? am i going to have to pull it off and reposition it?

[kb0nly]

Just a hair off isn't likely to cause a huge deal, i have actually had ones that i couldn't get perfect just how the sprocket/chain/cam line up they are not 100% perfect. All you have to make sure is the ignition timing is right and that you adjust the pickup coil/aka pulse gen to line up with the advancer when its set to the F mark on the flywheel.

My guess would be running lean since your idle is also erratic. Check your intake for cracking, did you replace the o-rings on the carb to intake and the intake to the head? They are generally flat and hardened and need replacement. Pull the plug and read it, see what you got for color.

[barnett468]

Hello


How did it run before rebuild?

What heat range is your spark plug?

How hot is it outside?

How old is gas?

Please list EVERYTRHING you changed during the rebuild ie cam, pipe, bored out cyl, carb compression, spark plug, etc.

As mentioned, I agree, it sounds super lean. I would not ride it until you correct it.

AIR LEAK TEST - Spray flammable brake cleaner LIGHTLY around intake using the long narrow nozzle at idle. If idle increases you have an air leak, if it does not then you don't.

[barnett468]

Hello


Does it have a flat spot upon acceleration from a stop or if you accelerate suddenly from a steady cruising speed of around 20 mph?

This is also a sign of a lean condition.

[Howdy]

Check for air leaks between the carb and head. A air leak could allow it to run erratically and also run lean and cause a red hot exhaust.
Howdy

[El Camexican]

If your cam timing is retarded by say a full tooth it could cause this condition, but start by checking for those leaks as others have advised.

PS. Are you sure your valves have enough clearance? May want to check that as well.

[Dave8338]

When you had things apart, did you replace the o-ring on the intake tube and on the back of the carb? If not, I would start there.

[TxPowderCoater]

double check for vacuum leaks, make sure the carb is operating and jetted properly and also double/triple check your timing since you have had it apart.

[hogmuffin]

Barnett: I replaced the cam with a good used cam. also replaced rockers with a good used set. new valves, new cam chian, new lower cam sprocket. i honed they cylinder and installeld new rings. I have a new plug, NGK DR8ES-L. Gas is fresh. it was about 70-75 out last night. valves are adjusted to .003 per tech manual. Thanks to everyone for all the advice. I will start with an air leak check.

[barnett468]

Hello



VALVES - Tight valves will not cause a pipe to glow red but if the leak test shows nothing than check them anyway.



PARTS CHANGES - Nothing you changed will cause the problem providing the used cam is original and same spec as the one you removed and the old plug was an 8 and the gear is an original. An aftermarket gear might be off slightly but if you were a tooth off on cam timing you could tell by how it ran.



FLOAT LEVEL - It is remotely possible it has developed a carb problem like plugged jet from tank degris etc. I would check it too.

[barnett468]

Hello



Don't forget ign timing as suggested by others.

Can you easily take a photo of the timing mark on the cam?

[yaegerb]

My guess is you are too lean. I have never seen a properly jetted 200x pipe turn cherry red from idling. Is it a stock 24mm? What are the jets you are running? Also the erratic up and down is likely an air leak like others have already stated.