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1990 YZ250WR to 2001 YZ250 Fork Conversion Questions

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I have done a number of fork conversions/upgrades to various bikes over the years. Some have turned out great (DR350 with DR-Z400 clamps and shortened 1996 RM250 forks) and some have turned a good bike into an ill handling Frankenbike (XR400 with 2006 CRF250R forks).

Here’s the project: I have a spotless 1990 YZ250WR with no more than 50 hours on it since new. For a number of reasons, I don’t want to sell it and upgrade to a later YZ (I also have a 1999 YZ125 and a 2001 YZ250).

I had the shock revalved by Noleen since Clark Jones probably know more about the early 1990’s YZ’s than anyone else. The shock works great!

The forks on the YZ250WR…this was the second year for the inverted fork, and it is a rather poor design with lots of stiction, harsh on the little stuff, prone to seal leakage and contamination, etc. The idea is to install a spare set of 2000 or 2001 YZ250 forks on the 1990 YZ250WR.

I am not worried about fork performance, but rather geometry/handling concerns. There appears to only be about 1/8” difference between the top of the fork tube and the centerline of the axle, so ride heaight will be OK. Also OK will be the use of the later stem although I’ll have to use the lower bearing from the later bike. The 1998-2003 tripleclamp will then mount right up.

THE QUESTIONS: Does anyone know the actual offset of the 1990 clamp or whether the offset is the same as the 1998-2003 YZ250 clamp? The other question is axle dropout distance, which affects trail. Does anyone know the dropout distance from the centerline of the fork to the centerline of the axle for the 1990 YZ and for the 1998-2003 bikes?

Thanks!

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I put yamaha forks on a KDX I had. I started with a triple from a 99 and ended up with a triple from a 2001. There was over 1/2 inch difference in the bar-positioning, with the bars being further forward on the latter unit. If I were to do it over again, I'd have saved time and money by buying an aftermarket triple with adjustable bar mounts. The fork offsets were so close I could not tell if there was any difference - but the bar mount positions REALLY make a huge difference in cornering. Even being aggressive with weighting the front end, the bike would push in corners, the later triples allowed the bike to turn effortlessly.

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I have done a number of fork conversions/upgrades to various bikes over the years. Some have turned out great (DR350 with DR-Z400 clamps and shortened 1996 RM250 forks) and some have turned a good bike into an ill handling Frankenbike (XR400 with 2006 CRF250R forks).

Here’s the project: I have a spotless 1990 YZ250WR with no more than 50 hours on it since new. For a number of reasons, I don’t want to sell it and upgrade to a later YZ (I also have a 1999 YZ125 and a 2001 YZ250).

I had the shock revalved by Noleen since Clark Jones probably know more about the early 1990’s YZ’s than anyone else. The shock works great!

The forks on the YZ250WR…this was the second year for the inverted fork, and it is a rather poor design with lots of stiction, harsh on the little stuff, prone to seal leakage and contamination, etc. The idea is to install a spare set of 2000 or 2001 YZ250 forks on the 1990 YZ250WR.

I am not worried about fork performance, but rather geometry/handling concerns. There appears to only be about 1/8” difference between the top of the fork tube and the centerline of the axle, so ride heaight will be OK. Also OK will be the use of the later stem although I’ll have to use the lower bearing from the later bike. The 1998-2003 tripleclamp will then mount right up.

THE QUESTIONS: Does anyone know the actual offset of the 1990 clamp or whether the offset is the same as the 1998-2003 YZ250 clamp? The other question is axle dropout distance, which affects trail. Does anyone know the dropout distance from the centerline of the fork to the centerline of the axle for the 1990 YZ and for the 1998-2003 bikes?

Thanks!

I have no idea on your specific question, but check one thing first. I dont remember which year it was, but one of the yz's from the early 90's had a massive steering tube. It was about large enough to throw an orange through. If your dealing with one of those, you might be hosed on nay triple changes.

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I have no idea on your specific question, but check one thing first. I dont remember which year it was, but one of the yz's from the early 90's had a massive steering tube. It was about large enough to throw an orange through. If your dealing with one of those, you might be hosed on nay triple changes.

Thanks for the heads up--I'll check to make sure.

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I know this thread is really old and the OP hasn't been logged on in a while but were you able to make the conversion work? I'm contemplating trying it on my 1990 YZ250WR but I'm not sure if I want to deal with a headache.

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