cb125s owners?

[wbks]

Thought I'd but this here rather then in the engine section because of the amount of cbs in bucket racing...
Started my cb today (took a bit), and it seems to have quite a loud rattle for the first 10 mins or so in the top end. It dies down a little after a while but its still there and seems to be a little more than normal top end rattle. But then again the only fourstroke I've ever owned was a zxr. Does that sound normal to anyone who has owned these bikes, and is it something to worry about? Other than that it ran reasonably well and it should be fun at mt wellintin this weekend

[F5 Dave]

Hard to say over the internerd but the cam chain tensioner likely needs adjustment/has run out of adjustment/or possibly needs a new chain &/or sliders.

[bungbung]

I agree with F5 Dave's suggestion of likely cause, cb125s don't rattle (normally)

[nudemetalz]

Tappet clearance too would be something to look at.

[F5 Dave]

Maybe it just needs adjustment. Some people weld an extension onto the tensioner if it has gone beyond adjustment, but I'd want to pop it open to see why.

[wbks]

Is there a chance that a blocked bleeder tube could have stopped good oil flow. I'm guessing adjusting the cam chain tensioner takes a bit of know how to do, which I don't have.

[F5 Dave]

virtually none at all required for know how, do a search on internerd honda's use similar setups for old tensioners & where they are located on back of barrel & how to adjust.

[Buckets4Me]

this is a cb125 single
and I'm guessing it has started doing this since you put new oil in ?????

it wasent synthetic oil you put in was it ????

[wbks]

I'm pretty sure it was...
it only had 600 or so ml when I got it so it didn't sound great then, either... So what oil is supposed to be in it? Would the wrong type of oil make the tensioner play up?

[Buckets4Me]

I dont know Ive got atf in mine

I remeber being told off by a cb man a few years ago when he sore I had
that thin type oil in my cb125twin (I think he likes running thicker mineral oils
but I'm up for being told I'm wrong)

do a search on the interweb for instructions
or wait for someone on here to let you know

[Sully60]

I'm pretty sure it was...
it only had 600 or so ml when I got it so it didn't sound great then, either... So what oil is supposed to be in it? Would the wrong type of oil make the tensioner play up?

No the tensioner is purely spring loaded mechanical type.
There's a small black rubber boot on the top of the crankcase on the left side just behind the cylinder, take the boot off and you'll see an adjuster screw and locknut, with the engine running loosen the locknut and wind the sdjuster screw in untill the engine stops rattling. Do the locknut back up and replace the boot, voila!

Does the crankcase not have the oil volume cast somewhere on the side. It should be somewhere between 800mls to a litre for that engine(don't quote me on that), there should be a dipstick take it out and just rest it in the hole, don't screw it back in if there's oil showing on the stick you should be ok.
Mineral 10w40 will be sweet, don't use any flash car oils they're not made for engines with the clutch and gearbox using the same oil.

[wbks]

Fcuked if I know about this mineral stuff, but it was definately 4stroke motorcycle oil, 10W40 or similar. K, I'll try that trick tomorrow, sully. Just so I know, does it matter if I rev it up and down while doing the adjustment? Or if I accidentally tighten it a little too much? And yea, I've got a liter of oil in it. Its all good being sinthetic, right?

[Sully60]

Fcuked if I know about this mineral stuff, but it was definately 4stroke motorcycle oil, 10W40 or similar. K, I'll try that trick tomorrow, sully. Just so I know, does it matter if I rev it up and down while doing the adjustment? Or if I accidentally tighten it a little too much? And yea, I've got a liter of oil in it. Its all good being sinthetic, right?

Just do it with the bike idling, you'll hear the rattle go away and thats just enough, lock it up there. I think you'll probably just wear the whole cam drive train a little faster if you overtightened it slighty, if you went all gorilla grip on it you could break the blade itself, use a little discretion and feel and you'll be ok. Just do the lock nut up tight, that's the one that counts.
Synthetic oils designed for bike engines would be fine if not a little overkill, sometimes in older engines you can get through synthetic a little quicker than the equivalent mineral oil and you don't see smoke like you would with mineral so you'll have to keep an eye on the level.
Cheaper oil changed more regularly is better than expensive oil changed less.

[wbks]

I only really got concerned at the rattle at revs but I guess the engine should be more quiet even at idle if I tighten it I guess? So if I tighten it not quite enough, but it doesn't rattle, its fine? Better a little loose than too tight?

[Sully60]

I only really got concerned at the rattle at revs but I guess the engine should be more quiet even at idle if I tighten it I guess? So if I tighten it not quite enough, but it doesn't rattle, its fine? Better a little loose than too tight?

Yeah, slightly loose is ok, loose enough for the timing to 'wander' too loose! The camchain will rattle more at idle as when the engine is revving and loaded the chain load is more consistant.
As said above check the tappet clearance as well.