Just picked up a GB400TT has developed a rattle

[Murray]

Thanks so much for the replies all.

The bike looks really nice, just has some mechanical issues.
I thought the tensioner might be auto adjusting, can it be adjusted externally? I can't find it in the gb500 service manual PDF I have. And don't see any bolts to loosen on the head. Is it that plug on the kickstarter side that looks like an inverted Phillips head?
Thanks again,

Alex

Check out this thread from ages ago - starts getting a bit interesting re your problem about post #47

http://www.kiwibiker.co.nz/forums/sh...-GB400TT/page4

[alexball]

Interesting little read that post Murray :-/
Got the rocker cover off on the weekend and found the timing chain to look good. Tight on the sprocket and the marks on the cam were very close to being lined up withe the surface of the head. The spring loaded tensioner wasn't installed correctly or had heavily worn as the spring had jumped out of where it should be and was levering on the side in the head. The one way roller bearing in the tensioner had a busted piece in it and one of the rollers fell out. I check out over the cam, bearings and rocker arms. The sub rocker arm in the right hand exhaust valve (decomp side) has a small amount of movement but when I measured tolerances they were just in spec. So I got a new spring and tensioner arm with the roller bearing and fitted it up today, also drained the oil and gave it a change. Had plenty in there. Put it all back together and found the rattle/jingle still there. Sigh. It's a very crisp sound compared to the rest of the valve train noise. Almost like its external. And it doesn't make it when it's cold. Intermittent at idle doesn't change with clutch in or out and get louder put to 3000-4000rpm then difficult to hear for higher rpm on both acceleration and deceleration. Any other ideas?

Alex

[unstuck]

Interesting little read that post Murray :-/
Got the rocker cover off on the weekend and found the timing chain to look good. Tight on the sprocket and the marks on the cam were very close to being lined up withe the surface of the head. The spring loaded tensioner wasn't installed correctly or had heavily worn as the spring had jumped out of where it should be and was levering on the side in the head. The one way roller bearing in the tensioner had a busted piece in it and one of the rollers fell out. I check out over the cam, bearings and rocker arms. The sub rocker arm in the right hand exhaust valve (decomp side) has a small amount of movement but when I measured tolerances they were just in spec. So I got a new spring and tensioner arm with the roller bearing and fitted it up today, also drained the oil and gave it a change. Had plenty in there. Put it all back together and found the rattle/jingle still there. Sigh. It's a very crisp sound compared to the rest of the valve train noise. Almost like its external. And it doesn't make it when it's cold. Intermittent at idle doesn't change with clutch in or out and get louder put to 3000-4000rpm then difficult to hear for higher rpm on both acceleration and deceleration. Any other ideas?

Alex

Did you find the roller that had fallen out? What was the condition of the guide like?

[alexball]

Sorry, the roller fell out on my desk while I was poking at one of the broken plastic pieces in the bearing. It was still working fine. The plastic guide? It was hard to tell with just a light shinning in to see but it didn't look chewed like I imagine it might. The front guide without the tensioner looked good also. I was going to get a new sub rocker arm and pin? For the decomp exhaust side next, but I'm doubtful that's it.

[unstuck]

Sorry, the roller fell out on my desk while I was poking at one of the broken plastic pieces in the bearing. It was still working fine. The plastic guide? It was hard to tell with just a light shinning in to see but it didn't look chewed like I imagine it might. The front guide without the tensioner looked good also. I was going to get a new sub rocker arm and pin? For the decomp exhaust side next, but I'm doubtful that's it.

Doubt it also, at least if it was within or close to spec.

[buggerit]

Sound seems very tinny, nothing to do with exhausts or heat shields with a bit of thermal expansion?

[alexball]

Sound seems very tinny, nothing to do with exhausts or heat shields with a bit of thermal expansion?

Yes it's a very crisp tinny noise almost sounds like there is nothing in the way to muffle/dull it, dosnt seem to happen when cold I believe, will check again tonight. What exactly are you talking about with the exhaust. I don't see any shielding. It's factory std. Jus pipes into the black box underneath to the muffler.

[BuzzardNZ]

Yes it's a very crisp tinny noise almost sounds like there is nothing in the way to muffle/dull it, dosnt seem to happen when cold I believe, will check again tonight. What exactly are you talking about with the exhaust. I don't see any shielding. It's factory std. Jus pipes into the black box underneath to the muffler.

That reminds me that one of my GB's had some kind of exhaust rattle. Been so long I've forgotten the specifics, but I do recall it sounded like there was some lose metal banging around in there. I never bothered fixing it.

[alexball]

might put some more kilometers on it over the weekend and see if anything changes. I forgot to mention I bought a leak down tester and it passed with very low leakage at TDC of compression while cold. Haven't tried it when hot.

[avgas]

Unbolt the exhaust from the collector box. I know this sounds strange as its fucken loud.......but you can hear if the rattle is coming form the muffler or not.

(Also take it for a blat around the block - sounds awesome for 30 seconds or so......any more and you go tone deaf or worse )

[Flip]

Many years ago I was a partner in a M/C courier company, we had many Gb400tt's, they were a great bike to use as a courier scoot.

It's probably the cam chain, they slowly start rattling from 30-80k km. After we started changing the oil every 3-4k we never had another one fail. I used to buy propper DID ones, break them and thread them in from the top. After a few years I used to do one in a couple of hours after dinner. I still have the tools to rivet cam chains some where.

We never had one jump a tooth they just started rattling and slowly got worse. I think I used to pay $110 for a cam chain.

From memory it was a relatively easy job to do.

[Murray]

Many years ago I was a partner in a M/C courier company, we had many Gb400tt's, they were a great bike to use as a courier scoot.

It's probably the cam chain,
From memory it was a relatively easy job to do.

Check post #17 - I think that covers it and maybe its not camchain. Mines (my wife's) in bits at the moment and made a similar intermittant noise that the mechanic thought maybe a bit of piston slap - however on pulling apart seems it could be more related to the broken cam chain guide - hopefully will be gone when put back together. Must say the barrel looked in super good nick.

Pulled apart to replace valve seals and rings as using a bit of oil and blowing a bit of smoke on start up and the mechanics treating it as a winter project. I got all the parts and hes odd jobbing the labour. Parts total about $470- including rings, camchain and guide, oil, all gaskets and misc items.

[Drew]

I would be checking that the inner skin on the exhaust headers hasn't come adrift.

Take the pipe off, and give it a shake.

[alexball]

Drew. Legend. It was the inner skin on one of the header pipes!!!!! I had just pull the rocker cover off and tensioner damper out to recheck everything again and had just loosened all the clutch side cover bolts when I realised I hadn't checked the exhaust. Explain why the noise was so tinny. So it's all back together and about to hit the road for ride with my rattly bike. My muffle is all beaten up so I might wait a few weeks and get a new headers and muffler. Thank you all, you been of much help

[alexball]

Pic.