Just picked up a GB400TT has developed a rattle

[alexball]

Hi All,
New member from Australia. I've recently picked up an import 1985 Honda GB400TT which was rebuilt in japan and I think probably not even ridden, as many parts look new and some things are missing, or DIY. After some googling this kiwi forum comes up a lot with some good GB info so here I am now. So I took it out on a long ride on Saturday, 200km. The last 30min of the ride she developed a rattle. I put a video up on YouTube to help. Before the ride I checked and adjusted the valve clearances, they were only a tiny bit off. My mate I live with also has a GB400 and his doesn't make this noise, in the video you has hear it come and go.

Link to YouTube: http://youtu.be/BFcPJoCIc_E

Any ideas? Something to worry about? This is my first bike so I'm a bit of a newb but have spent Tim working in cars so know a little.

[BuzzardNZ]

Cam chains are known to go in these things.
The last GB400 I had needed a new one and sounded a lot worse than yours.

[alexball]

Cam chains are known to go in these things.
The last GB400 I had needed a new one and sounded a lot worse than yours.

This is typical timing chain noise then BuzzardNZ?

Thanks for the prompt reply,
Alex

[avgas]

This is typical timing chain noise then BuzzardNZ?

Thanks for the prompt reply,
Alex
Yep - cam chain. But in saying that - you probably have a good 5,000 km before it will actually snap. As Buzz said......they get REALLY loud. If you wanted to risk it - change the oil and see if it gets louder or quieter.

Shouldn't be too expensive to replace. I think mine were all due around the 100,000 mark. So how many km does this have?

Its a good time to check the rest of the bike if cam-chain is due - are the forks leaking?

[unstuck]

Cam chain tensioner perhaps has moved, try re tensioning it and see what happens.

[BuzzardNZ]

Shouldn't be too expensive to replace. I think mine were all due around the 100,000 mark.



I've owned three GB400s. Can't remember how many k's I did on the first two ( no problems with rattling ), but the third one only had around 40,000 k's on it when the cam chain started to get very loud and rattly and needed to be replaced. I think it cost about $700 for the job and this was around 8 years ago.

[HenryDorsetCase]

Can they do it without taking the head off?

If the head has to come off its time for some extra CC's, bigger valves, and Keihin flatslides. Bonus: when the camchain starts rattling you won't hear it over the slides in the carbs......

nice looking bike from what can be seen of it.

[alexball]

Thanks so much for the replies all.

The bike looks really nice, just has some mechanical issues.
Odometer says 22'000km, I think that's unlikely. I think the bike has been fixed up from a crash from what I can tell, lots of random new parts and dodged DIY painting. The engine has been painted with regular silver paint, which melts when the it's heated up. Tank has been resprayed blue/silver ala 87/88 special edition and side covers are from a Special Edition but it's actually an 85 GB400F.

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?

Finally. Parts. I can't find much on ebay. There none in Australia from what I've found so far, but some XBR500 parts have fitted. Master cylinder rebuild kit was the same. Is anything available in NZ?

Thanks again,

Alex

[avgas]

I've owned three GB400s. Can't remember how many k's I did on the first two ( no problems with rattling ), but the third one only had around 40,000 k's on it when the cam chain started to get very loud and rattly and needed to be replaced. I think it cost about $700 for the job and this was around 8 years ago.
Ouch!
Yeah i had 2 x 87 and 1 x 88. Only had to do 1 camchain myself at 114,000 (cost me about $150-250 over 10 years ago.....but was a cunt of a job to do.....or I was doing it wrong:rolleyes:). One I never did (got wrecked before it needed one). The other 1 had just had theirs done at about 90,000 est.

On the second one I found the sweet spot was using really good oil regulary. Visco 5000 every 5-10K. It went a good 70K before a rattle (I got that one @20K).

[avgas]

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?

Finally. Parts. I can't find much on ebay. There none in Australia from what I've found so far, but some XBR500 parts have fitted. Master cylinder rebuild kit was the same. Is anything available in NZ?

Thanks again,

Alex
Tensioner = spring from recall. You adjust it by making spring tighter. (I might be getting confused with my SRX though)
Parts - honda can still get them in. But check the other sister motors (XR400 / XL) as they shared some parts. If your gonna chuck coin at it - I highly recommend some IKON shocks (ex-KONI) as they are worth gold.
Spark plug is up top and front. You will smack you hand on the tank getting it out. Chuck an iridium in there so you don't have to take it out often.

Oil filter is held in buy 3-bolt plate on side from recall. Once again I think the filter is same for XR400.

Electric starter still work? If so I give it another 20,000 km and it will die.

[Murray]

Thanks so much for the replies all.

Finally. Parts. I can't find much on ebay. There none in Australia from what I've found so far, but some XBR500 parts have fitted. Master cylinder rebuild kit was the same. Is anything available in NZ?

Thanks again,

Alex

Call malcolm at econohonda NZ 07 884 8810 or http://www.econohonda.co.nz/

His part list is out of date but he can generally get anything

My GB400 1988 is in parts at the moment - new rings, camchain, carb jet, sprocket seal etc

The cam chain guide had also snapped which was giving an intermittant clicking noise so one of those needed as well

Malcolm had all the parts to me in a matter of days.

Note a GB400 Head gasket doesnt come in a set its single item only. The GB500 gasket set contains all the parts to fit a GB400 apart from the head gasket - bit of a pain but Malcolm swapped the gaskets over and gave a discount

[BuzzardNZ]

On the second one I found the sweet spot was using really good oil regulary. Visco 5000 every 5-10K. It went a good 70K before a rattle (I got that one @20K).

Yeah, I was told to religiously change the oil on these. I'm not sure why this is especially crucial for large singles but I did it anyway and never had any issues with my first one. The last one was in a pretty bad way when I got it and I only did about 1500km on it before the cam chain started getting mega loud.

The second one was a sorry story. A nice find with only 3,000km on the clock, garaged for ages ( 5+ years ) and in showroom condition. I wrote it off a week after buying it due to slipping on an oil patch right outside Wellington hospital, which was handy as I just walked in and they put a plate in my broken arm. I was able to be fixed but my lovely GB wasn't :crybaby:

[jasonu]

Has the powerband been serviced recently?;)

[alexball]

Thanks so much thus far all :) I thought I was all alone with very few of these bikes in Australia. Went for a short ride today and I can distinctly hear it when accelerating and decelerating. Can I put the motor at TDC and whip the rocker cover off and back on without immediate need for a new gasket? Would like to see if the tensioner is still there and operating.

While setting the valve clearances I also found the flanged crank bolt has a quarter of the flange sheared off and the head of the bolt has lost a mm like it was belted with a hammer. Possibly someone's had the side covers and dropped the motor? Odd.

Thanks for the link to econo honda Murray.

BuzzardNZ that's a terrible end for such a nice GB!

Alex

Ps. Are these meant to rev well past 8000rpm on the gauge, seem to get to about 9000 if that gauge reads true.

Pic of bike and sheared bolt attached.
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299632

[unstuck]

Hard to be accurate from that vid, but looks like it has already had some sealer around the rocker cover, so a little more wont hurt, not ideal but better than having oil running down the fins. :2thumbsup

[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/showthread.php/12860-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. :scratch:

[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 :laugh: or worse :Police:)

[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.
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[unstuck]

I love a happy ending.:love::love::Punk::Punk: