Vintage Dirt Bike Q & A

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PostPosted: Sun Dec 18, 2016 5:44 pm 
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Joined: Thu Nov 03, 2016 3:54 am
Posts: 28
I’m a couple months into fixing up the 74 MT250 and although it’s becoming a bit of a money pit, and my torpedo heater in the barn has been giving me fits, I’m determined to have it ready for Spring. If you’ve any feedback or answers to the following I’d greatly appreciate it:

a) I’ve cleaned a couple pounds of sludge out of the forks and replaced the piston rings and seals therein. I’ve opted to replace the feeble fork springs with Race Tech springs .43 @ 500mm in length. The pre-load is more than RT’s resident genius (a very nice guy) would like, but he said it’s all good (given my and the bike’s combined weight) as long as I’m not jumping any fountains with the bloody thing. Some shorter fork caps would lessen the pre-load; but damned if I can find any. Does anyone have any experience with using modern springs in these forks?

b) The front wheel was bent a bit and despite my efforts with a BFH and a vise, it remains so. I found that the hubs of the XL250/350 for part of 1975 and all of 1976 are identical to the MT250, so I bought a couple of nice examples (front and rear) for damn good prices. However, the crush drive in both the MT and XL rear hubs are essentially disintegrated. I really don’t want to drop another 50.00+ on some fancy rubber parts; has anyone succeeded in making some out of an old tire, etc.? If it’s thought to be a safety issue I guess I’ll pony up the cash.

c) I paid an OBSCENE price for chain tensioner with a roached roller (just try to find one!). [b]Does anyone have any experience with retro-fitting an aftermarket roller of the same diameter?
[/b]
d) The throttle cable was badly frayed near the grip and the only example of NOS I could find was some clown that wanted a 180.00 plus shipping from the UK. I found an aftermarket one from Japan (all in price + shipping) 65.00. So, persistence in searching for parts for these old bikes sometimes pays off. :D


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PostPosted: Sun Dec 18, 2016 6:47 pm 
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Joined: Fri May 29, 2015 7:34 pm
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I didn't know that there was a tensioner on an MT. Must be aftermarket?
It would probably be pretty simple to machine up a roller.


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PostPosted: Sun Dec 18, 2016 7:23 pm 
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Joined: Thu Nov 03, 2016 3:54 am
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Killer Canary wrote:
I didn't know that there was a tensioner on an MT. Must be aftermarket?
It would probably be pretty simple to machine up a roller.


Nope; it's a stock part, and from what I can tell running the bike without one risks throwing a chain.


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PostPosted: Mon Dec 19, 2016 3:17 pm 
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Joined: Tue Jan 27, 2004 8:51 pm
Posts: 136
Location: Gilbert, AZ
The three mt250's that I have owned only had a fixed guide with a roller on it, not a tensioner. When you say chain tensioner we think a spring-loaded wheel or block. Does yours have a spring-loaded tensioner or a fixed roller on a guide?

If you have the fixed roller (stock honda guide picture is attached) and just need the roller go to a skateboard shop and get some free used ones from them with bearings. You may need to be creative hand grinder size down some and you could even grind a ridge in the middle to protrude into the chain rollers slightly.

As for the throttle cable, if you're housing is ok make your new insert with a bicycle cable that you can buy for just a few bucks and some creativity. You can replace all 3 inserts, if needed, this way.

My advice is to pay for the OEM Honda parts for your rear wheel.
In the early 1970's I ran my CT90 with worn-out rubbers which ended up breaking the hub...3 times. I guess I was a slow learning kid.

Rick


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PostPosted: Mon Dec 19, 2016 6:09 pm 
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Joined: Thu Nov 03, 2016 3:54 am
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Thanks Rick. I'll take your advice and buy the OEM rubber inserts and save myself the grief. As far as the chain guide goes, I was going by the 74 parts guide that calls the roller a tensioner. Though I'd agree without a spring it certainly isn't a dynamic tensioner that comes to mind when one uses the term.

Thanks again!

Al


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