Bah my honda xl125r rattles like a ********!

[marc1024]

Few months ago i passed my CBT and im now currently running a wee honda xl125r. Before i passed my cbt i seized the eng...i mean the engine seized up on me, one of the valveguides got twisted and then boom. The week after we bought lots of new parts for the top end, including a new piston, rings and gasket set. Engine ran well but it was mega rattley and my dad didnt trust the engine So he bought a new one. That engine was 2 years older (1982) and it ran perfectly! then all of a sudden a high pitch rattle started coming from it. Cam chain was tight (not to tight) and tappets where set right. Oil level was perfect.

Now we have decided to put all new parts from the old engine onto the newolder engine. The rattling is still there but it isnt as bad. Anyone got any ideas ? my dad is wondering about how to time these engines. There is 3 marks on the flywheel which he has timed them accordingly but still nothing.

We do not have a service manual to look up anyone got any ideas???????? help will be very much appreciated!

Iv kept it well maintained. Yet it have mega problems

 

[PardonTheWait]

To be honest, that's probably always going to rattle. Bikes like that do, both my MX bikes were rattly, so is my Pegaso 650 (big single)

Also, that's in exceptionally good shape! Nice work

 

[marc1024]

To be honest, that's probably always going to rattle. Bikes like that do, both my MX bikes were rattly, so is my Pegaso 650 (big single)

Also, that's in exceptionally good shape! Nice work

its just when we got the other engine, trying to get it sound like that when we first got it is impossible. the engine was smooth idling and silent on high revs! it sounded like a new engine.
I use the bike nearly every day ( about 40 miles a day ) and being into kart racing, hearing a rattly engine is scary to me.

Thanks i like to keep everything looking good.

 

[Dogbreath]

How on earth does a valve guide get "twisted"?

A "rattle" isn't very descriptive though - is it a regular engine speed related noise? Does it get worse under load?

 

[marc1024]

How on earth does a valve guide get "twisted"?

A "rattle" isn't very descriptive though - is it a regular engine speed related noise? Does it get worse under load?

its constant loud rattle no matter what speed or revs or gear. if anything it sounds better idling. I cant describe the sound well, i could say its a high pitch rattle?

The rattle is coming from top end of the engine, the reason were confused is if the timing was out it wouldn't start first kick. Exhaust note is sweat and smooth with no miss fires.

don't ask me how, the valve guide was completely mangled. this was the first run out with it since we got it so we had no clue how the bike was. when taking the head of to see the problem when it seized. the chain tensioner was snapped, rockers where worn in the wrong place ( i couldn't tell the difference but my dad could) and the cam shaft was worn quite badly. Piston was totaled. no damage on top but massively scratched around the sides, all the rings where damaged in some way or another.

 

[Dogbreath]

Sounds very much like a loose cam chain to be honest, even though the tensioner feels tight. It's possible the tensioner blade has broken.

 

[ShakenNstirred]

How on earth does a valve guide get "twisted"?

A "rattle" isn't very descriptive though - is it a regular engine speed related noise? Does it get worse under load?

i cant see how it can, in my experience there very hard n brittle, they break and not twist or bend

sound like a cam chain guide, if warn the little lip in the centre that keeps the chain centred can wear off letting the chain move sideways and rattle on the cam chain tunnels
there only a hard rubber so do wear off, the chain tension will look fine

 

[marc1024]

i cant see how it can, in my experience there very hard n brittle, they break and not twist or bend

sound like a cam chain guide, if warn the little lip in the centre that keeps the chain centred can wear off letting the chain move sideways and rattle on the cam chain tunnels
there only a hard rubber so do wear off, the chain tension will look fine

http://images.cmsnl.com/img/products/guide-cam-chain_big14611300000-01_6d8f.2jpg[/IMG2][/QUOTE]

I will try and get pictures of the old valve guide to show you exactly what happened.

the lip you are on about is quite worn. well on the old engine it was badly worn down, then when we rebuilt it we replaced it all and it still rattled.
In the new engine (current one in the bike) after putting all the new bits on the old engine onto the new we changed the tensioner as well and the small thing that adjusts it. Chain is defiantly tight and if you put something down the chain tunnel and try and move it, it has about 0.5 cm of play either way then again whos to say that doesn't change when the engines running?.