TIP OF THE MONTH: HONDA 350 Twin Motors 1968-73
STRENGTHS
CB/CL 350 engines are
very strong by design and therefore very dependable. The crankshaft, main
bearing and big end rod bearings are all heavy duty. The primary drive utilizes
an offset straight cut gear design, rather than a chain. The clutch is strong,
as is the five-speed transmission. The over square engine allows for free
revving to high RPM's. What really gives this machine good reliable output, up
to 36 hp, is good design. Valve sizes, valve angle, port and combustion
chambers were all designed for good breathing. Overall, the 350 twin motors are
good reliable trouble free machines.
WEAK POINT
The CB/CL 350 engine
was engineered very well, having virturally no weaknesses when new. However,
early engines did suffer from premature cam lobe and rocker arm failure (as did
any 10,500 rpm engine 1968-71). Now being up to 36 years old, all engines are
subject to carburetor diaphragm failure. All rubber parts fail due to age. Be
sure to check the cam chain tension roller, cam chain roller and cam chain
guide.
RECOMMENDATION
When cleaning the carburetor use extreme
care while removing the diaphragms from the body. Inspect for cracks and tears
(replace if damaged). While the engine is still in the bike, remove the cam
chain adjuster and check for chain roller damage. If you find damage, it's best
to get a top end job and replace cam tensioner/roller, crankcase roller and
chain guide. If the engine has 25+ thousand miles, it's best to replace the cam
chain also.
PERFORMANCE ENHANCMENT
Honda 350 engines respond very well to the time proven
performance updates. The cylinder head can be worked to improve flow with great
results. A number of cam grinds are available with track proven performance.
These engines can yield very good output, yet still maintain their reliability.
The 350 is one of the most popular motors for vintage road racing.
( Mirrored from - http://www.mginproducts.com/Professional%20Tips%20and%20Tricks.html )