Jump to content
Sign in to follow this  

SL 125 engine noise

Recommended Posts

Need some insight here. I have been working on this old SL for a while. I replaced the cylinder with a new stock bore cylinder including piston, rings, wrist pin. Got a like new CL 100 head with valves and cam that look like new. Bolted everything together and the bike started and ran well except for a noisy taptaptaptap that was way too loud to be considered normal. Reverified the valve lash adjustment and still no luck. Pulled the engine, tore it down. Piston is installed correctly. no sign of metal to metal. Re verified all parts were well withing service limits and all looked great. Re assembled, installed and with the valve covers off if I kick it over slow I can hear a tap when the intake valve opens fully.

I haven't restarted the bike because I do not want to risk damaging the engine. The CL 100 head only had about 4300 miles on it. All surfaces of the cam and journals look like new, rockers look good, valves looked new and again no sign of anything hitting the piston or anything else.

Am I missing something here?

Many thanks in advance for any helpful insight.

Regards,

RRR

Share this post


Link to post
Share on other sites

Greetings R3,

Just finished rebuilding the wife's ride which is a started off as a CL125, so I'm familiar with the engine, in CL form anyways.

Am I missing something here, why was a CL100 head substituted in the first place? I wasn't aware that they were interchangeable.

My guess is the heads are different in design height and you're probably running the piston into the valve. I realize you haven't seen any marks but since you haven't run the engine it is possible.

It's also possible that the CL100 might have more lift on the cam than the SL125 unit, this could be for a variety of reasons, like say a non-stock cam.

Good Health to You and Yours, Ross59

Share this post


Link to post
Share on other sites

Greetings R3,

I've a 100 head in the shop, I'll check it against the one on her bike and let you know tomorrow if there is anything that "jumps out" that appears incorrect.

Later, Ross59

Share this post


Link to post
Share on other sites

speculation on my part, but although all of these heads seem similair there must be differences, however slight and I think that is what you have encountered. Ross 59 is onto something and I agree with his conclusions. As an example, the TL125, is (so I am told) way different than a SL or XL125, as an example. Stroke is different and so is the cam.

Dwight Rudder has alot of experiece on these maybe he can chime in and find you oddity.

Share this post


Link to post
Share on other sites

ross59 and motosprtman - My bad.... I just rechecked purchase info on the cam and head, valves etc and they were from an SL 100 not a CL 100. The only difference I am aware of between a SL 100 and SL 125 is a slightly smaller combustion chamber/dome. I believe this swap has been done many times before with the only change being a little boost in compresson. In regards to me not running the engine..... I have in fact started and ridden the bike for about 10 minutes before I tore down again for investigation, I have not restarted the bike since the 2nd tear down looking for the source of the noise. I would think that a 10 minute ride would have shown some signs of metal to metal contact on a new piston.

As always many, many thanks for your replies and suggestions

Regards,

RRR

Share this post


Link to post
Share on other sites

I wonder if a sacked valve spring would be the cause, make for like a sticking valve on the return ? just a WAG on my part.

Share this post


Link to post
Share on other sites
Probably Cam Chain. If the cam chain is still good you need to adjust it properly.

Thanks Dwight,

While he cam chain is not new it seems to be servicable. I have messed with the adjustment when it was running after the initial rebuild with little to no effect. The sound is different than swirling sound sound I associate with a cam chain that is out of adjustment. It's a definate tapping sound that is louder than the exhaust.

Thanks for the input. And if I have to pull it again I am going to change the chain just to be on the safe side.

Regards,

RRR

Share this post


Link to post
Share on other sites
I wonder if a sacked valve spring would be the cause, make for like a sticking valve on the return ? just a WAG on my part.

Thanks Motosprtman. I have given that some thought as well. I am unsure how I can verify that without pulling the valve and unfortunatly I am living about 6 hours from my shop while my wife finishes school. If I were home I could make a valve compressor tool and.......

Any ideas how I can check that without pulling said valve, springs etc. I have looked inside and can not see anything out of the ordinary, but then again I am just comparing the exhaust and the intake visually using a flashlight thru the opening.

Regards,

RRR

Share this post


Link to post
Share on other sites

Bent cam chain sprocket tooth? Turn it over by hand or by the flywheel bolt and see if you can pin it down to top or bottom end or one side of the engine or the other. Better yet use a variable speed drill.

Share this post


Link to post
Share on other sites
Bent cam chain sprocket tooth? Turn it over by hand or by the flywheel bolt and see if you can pin it down to top or bottom end or one side of the engine or the other. Better yet use a variable speed drill.

Thanks drturnip, I have it narrowed down, at least I think I have. It seems to make the noise when the intake valve opens. I was thinking about it today and I could be wrong but doesn't the intake valve open on the "down stroke" of the piston? If so that would seem to eliminate the "valve hitting the piston" theory. As I said before, there is no evidence of any contact between the piston and valve after a ten minute ride. Then again, I am a novice at this and take every question/suggestion/educated guess seriously. So to all who have responded, many, many thanks and do feel free to keep the suggestions etc coming.

I will look at it again tomorrow with a clear head and see if something looks different. Still wondering if I can verify the spring etc without removing it,

Asalways, I am in debt for all your sage advice.

RRR

Share this post


Link to post
Share on other sites

You may have a sticky or bent valve. It might be hanging open long enough to create a gap between the rocker and cam then it lets loose causing noise. Did you remove the valves from the head? I am pretty sure the head needs to come off.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×