QuestionQUESTION: I have a 1972 Honda SL350 with 8K miles which I have not ridden in a few years.I stopped riding it because the valves or cam chain sound really loud to me. I recently reset the valves and adjusted the cam chain and it still has alot of mechanical noise. I believe it has an automatic cam chain adjuster. I have had people tell me that these bikes always sound like this but it sounds pretty bad to my ears. I think I saw somewhere that newer adjustable cam chain tenstioners are interchangable? Would this help or is the bike supposed to sound like this. When I adjusted the valves I made sure the timing marks lined up where they were supposed to, but they did not naturally sit where they needed to be. I had to have another person hold the flywheel in position while I adjusted the valves. The valve springs were tight where it naturally sits, about 1/4" counterclockwise of the marks, and the valves could not be adjusted enough for the correct settings. Is this correct? I did set the timing and point gap as well. The bike starts first kick. Thanks.
ANSWER: Cody, reference here...
http://www.cmsnl.com/honda-sl350-motosport-350-k2-us_model734/partslist/E++06.ht
There are no automatic adjusters for the 350s, other than the original 1968 models, which were updated immediately.
You could have a broken tensioner blade, a worn out cam and follower set due to oil restrictions. There are tech bulletins on 350s for defective side cover gaskets for the bottom end, which will starve the top end of lubrication. You should be able to adjust the valves on TDC for each side, even if the engine wants to rotate a little beyond that point. The engine turns forward due to the opposite side cylinder's valves being open, loading the camshaft.
Rock the crankshaft back and forth with a pair of vise-grips on the bolt. You can feel if there is slack between forward and backwards, if the camchain is still loose. Watch the end of the camshaft, while you are doing it. The crankshaft and camshaft should always be moving at the same moment and in the same direction with no lost movement.
Check the tensioner for a binding tension rod. Pull the tensioner off and inspect the roller inside. Drain the oil and clean the oil filter looking for debris of some kind. The type of debris will indicate the possible causes... magnetic filings are probably from the cam/followers. Aluminum shavings are often from the area around the loose camchain. Black rubber plastic parts are from the tensioner/roller.
If you can't get the valves to adjust to specifications, then the camshaft/follower is worn out.
Note that there are shims used to reduce the endplay on the camshaft, in the end covers. If the cam is walking back and forth, in addition to rotating, you will get noise. Hopefully, your camsprocket bolts haven't sheared or some other misfortune.
Bill Silver
---------- FOLLOW-UP ----------
QUESTION: Well, I pulled off the cam chain tensioner and the roller was pretty ate up. Does not look like it would turn very well. As far as I can tell, the only way to replace it is to remove the cylinders? If so, I might as well rebuild the top end huh? Any thing I should look for, what should I replace, and does anyone make an aftermarket cam chain tensioner so this does not happen again. I do like a good project! Thanks!
AnswerThe tensioner parts are wedged between the head and cylinders and crankcase, so the motor comes out and top end off. There is a racing slipper-type tensioner setup, but they are not cheap. A fresh OEM unit will last many years. The damage can come from age as well as use or misuse.
Look for oil contamination in the filter system and check ring gaps when the pistons are off. Unless it sat for a long time and the rings got stuck in the grooves, it should just be a good cleanup and reassemble with fresh parts.
I just got in a new front camchain guide for this engine, listed on Ebay today. Don't have the other parts, though.
Bill Silver
