Top End Rebuild

[No Worries]

Long story short, I had a leakdown test done on the CBR and air was leaking out the exhaust. I took the head off and the exhaust valves were burnt. It sat for several months while I rode the GS1000. I bought new exhaust valves and started fixing it today.



I cleaned the cylinder head on the right. I also lapped the right exhaust valve seat. Check out the difference. I'll clean the other cylinders tomorrow. I'll also lap the intake valves. I bought new valve guide seals, gaskets, and a new cam chain tensioner (CCT). I should finish it this week.

[BobTheBiker]

good start. the CCT killed it the first time didnt it? or was it the burnt valves?

[Dave]

Originally Posted by BobTheBiker

good start. the CCT killed it the first time didnt it? or was it the burnt valves?

dead valves make me think of fueling issues. check your carbs and spark lately?

[BobTheBiker]

Come to think of it, I believe he mentioned somewhere awhile back that the ignition gave him some kind of troubles, so spark is probably a culprit.

[No Worries]

Originally Posted by BobTheBiker

good start. the CCT killed it the first time didnt it? or was it the burnt valves?

Older CBR's had a problem with CCT's. On the 600's, the CCT is on the outside of the engine and can be easily changed to a manual adjuster. The older 1000's, like mine, have the CCT under the cams.

Originally Posted by Dave

dead valves make me think of fueling issues. check your carbs and spark lately?

With most of my riding above 6,000 feet, lean conditions are rare. Exhaust valves usually burn when the valve can't transfer heat to the seat. Usually caused by a too tight clearance, if just one valve is burned, with the valve being held off the seat. If all the exhaust valves are burnt, the chain skipped a tooth and/or the CCT ain't working.

Originally Posted by BobTheBiker

Come to think of it, I believe he mentioned somewhere awhile back that the ignition gave him some kind of troubles, so spark is probably a culprit.

All bikes will have electrical problems sooner or later. When I couldn't beat the new liter bikes anymore, I cleaned the carbs. When the condition continued, I checked the ignition advance. Since I'm the only person on Earth who has and still uses a timing light, I saw that the ignition timing stayed at TDC while revving the engine. The pulse generator went bad. I bet it's a common problem. The bike starts and runs, but has no snap and the mileage goes down.

[BobTheBiker]

thats a hell of a strange place to put the cam tensioner. and to think I was pissed that the engine is split in two by the cam chain.

[Dnyce]

Originally Posted by No Worries

Since I'm the only person on Earth who has and still uses a timing light.

not true old man lol-i own and use one for the kz. gd tuning tool