Vintage Dirt Bike Q & A

Does anyone have any advice on fork oil for the MT250? I can follow the manual, but would i be better off with a different weight of oil and more/less of it? Thanks.

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MT250 with CR250 top end & Bassani pipe... almost fully restored.

See more of my motorbike builds at my Honda MT250 and Yamaha RD and RZ website, 2Smoked.com

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depends on your weight, what you like and if you have original springs or not. I weigh about 185 and have original springs on my MR250. I mix 10 and 15 weight fork oil to get approximately 12 weight oil and use about 1/2 oz more than manual calls for. That is just my preference. The atf called for is approximately equivalent to 15-17 weight fork oil, from my studies.

I had read that ATF is equivalent to 7 weight oil.

I plan to try 10 weight fork oil next.

~JM~

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Big Block Cadillac Forum

Assuming it's factual, this is an excellent page:

http://www.peterverdonedesigns.com/lowspeed.htm

It appears every oil is different, but as a general rule atf (doesn't say type F or Dexron or whatever) may be somewhere close to 34 cSt @ 40, which is ballpark to many fork oils around 10 weight. But if you look closely, one atf is somewhere near 53cSt and different fork oils are kind of all over the place, too.

On the older bikes, when people say ATF, I kind of always assume they mean Type F. Don't know if there is much, any or a lot of difference between that and Dexron.

Other charts I've seen hold out that Type F is near 15 weight of modern fork oils. But doesn't look like any two oils are quite the same anyway.

I guess in the end, you spend a little time and money experimenting with different weights until you get something close to what you like.

Cool! Thanks guys, i will have a read and let you know what I do

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MT250 with CR250 top end & Bassani pipe... almost fully restored.

See more of my motorbike builds at my Honda MT250 and Yamaha RD and RZ website, 2Smoked.com

If you like watches, check out my websites: DeskDivers.com & PloProf.com

I run 10w in the forks... and also (this may not be the best thing) made 2" spacers for each fork out of PVC pipe.

The original springs are quite tired and there is no real adjustment to preload other than shimming.... plus, for my 'mildly aggressive' woods rides, I need to have my front wheel planted on wet stuff.

I recommend doing it if you're over 180lbs, but be VERY careful re-installing the fork caps...

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I drink your milkshake!

Danny, thats a good idea mate, thanks for that. Can I ask what size pipe you bought?

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MT250 with CR250 top end & Bassani pipe... almost fully restored.

See more of my motorbike builds at my Honda MT250 and Yamaha RD and RZ website, 2Smoked.com

If you like watches, check out my websites: DeskDivers.com & PloProf.com

Today I finally did my forks... put a 1mm washer on top of the spring to make sure the spring sits nice against the extra 2cm of PVC pipe as a spacer. no way could i get 2inches in there LOL. Also whacked in 146*ml of fork oil... good quality Motul stuff, 100ml of 10weight and 46mm of 15weight to give me a mix. Forks seems much better than they were.

Same time I swapped to my spare wheel with an alloy rim, probably an XL wheel as it has a speedo drive. Spent ages removing the old crappy tyre and fitted a lightly used tyre from my modern KTM wheels which im not using as that bike is becoming a supermoto and getting a differnt engine...

* chose 146 as my syringe doesnt measure odd numbers very well LOL. I hardly think an extra ml of oil will matter either way, but i wanted them the same...

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MT250 with CR250 top end & Bassani pipe... almost fully restored.

See more of my motorbike builds at my Honda MT250 and Yamaha RD and RZ website, 2Smoked.com

If you like watches, check out my websites: DeskDivers.com & PloProf.com