1978 WR250 17 inch wheel and other questions

I'm in deep on a '77CR250 resto, but I could not resist picking up a 1978 WR250 on the cheap. A few initial questions:

1. 17 inch rear wheel. Do people stick with that size and somehow find 17 inch rims to re-lace or do people convert to the more readily available 18 inch size?

2. What size rear shock did this bike come with? There is a 16 inch eye to eye dual spring shock with cooling fins and a Schrader valve on it now.

3. Crank shaft is frozen so I'm going to need a rod kit for a crank rebuild. What's my best option?

I like your user name. I had that happen yesterday though not on a bike in this section.

There are places that take blank rims and create the spoke holes that would be the answer to somehow. I do not do restoration and if I did probably would want an original rim.

I think the shock you are describing was aftermarket, I had a set like that with the fins but it had 3 springs, sold them to someone local years ago I think I saw a set go for like $300 on ebay a few years back.

Is a used crank or used lower ends considered an option? You did not put a location in your profile.

If you are going to ride 18'' rims make better sense due to choice of tyres, in the UK even a half decent 17" tyre is not available!

For some reason I cant seem to quote a post, but Frank you must have been at the B&B. I'm in RI. I had a family commitment and could not make it. Used bottom ends or cranks are an option, but I tend not to trust old bearings, so Id rather rehab what I have, unless someone had a trustworthy crank.

That was my thinking, but looks like IRC makes a nice 17 inch tire so problem solved there.

I can not quote in internet explorer. The function works in Google chrome. This forum has been the least problematic of the few forums I am a member of until lately.

strip the motor, you may find its not too hard to rebuild. if the big end is seized, you may simply be able to fit new pin and rod, new bearings and seals. should be an easy job

Yup, no stranger to motor rebuilds, just wondering where others source the rod kits. I like to supply the rod kit to the machine shop.

Holy cripes - I just did some surfing and they want $350 for a rod kit at a certain vintage parts site!!! If this is the only option that is a game changer and makes me want to take a chance on a used crank. There is an entire engine on ebay now for $400!!

Absolutely no reason to go to an 18" rear wheel, the IRC Vulcanduro is as good as any tire for an 18". Dick Burleson won 6 of his 8 National Enduro Championships on a 17" rear wheel, so how bad could they be?

Yes I have no issue with vulcanduro and good point on King Richard. Looks like both excel and sun offer 17 inch rims that will work.

In the past I ran trelleborg ten masters in 17" rims. But there not available. I did start using the IRC volcanduro ve33 510:17 rear tires. Watch for sales on the v33 17" tires.

Note, I never seen tires as tough as the trelleborg ten masters. For the 18" rims the IRC M5B 140:18 or the IRC v33 volcanduro 5:10-18". I always install both rim locks.

But the entire engine will need rebuilding too. Find a crank on eBay.

$350 is a great price here within the USA. From abroad significantly higher. You are dealing with vintage, it is not mainstream production and it comes under the luxury realm that includes high end Euro autos, aircraft, marine, Unless you know what to buy and having the equipment to alter to needed specs without sacrificing component integrity, just pay what it costs if you really want to play. You do not have choices when the parts you need have been out of production for over 20 years

Unless you can check the rod on an engine you are buying there is no guarantee you are getting a good one. I bought a bundle of Husqvarna basket cases that I had to buy sight unseen. Out of 4 bottomends, 2 required rod replacement.

thanks Jim but I still feel that is very high I have done quite a few vintage bikes with parts that have been out of production. Just my opinion.

I actually purchased a 84 250CR crankshaft a few years ago on eBay that the seller verified the integrity of . I can use the rod to rebuild a 430WR crank I have as the rod is the same for the primary kick 250 & 430 engines.

In your case you can likely use a rod from a 75 and up 360 or 390 crank as I have heard here recently the stroke difference is controlled by the offset from center and the flywheels are the same base diameter.

Shock should be 15 inches eye to eye

If you have a 77, you should have a 18" wheel to try out.The 78 has a 18" test them both and you decide.PM me and I can set you up with a rod option.

Call Halls cycle. They are very good with vintage stuff. I got a rod kit from them last year, I think it was $250. Also try Paradise cycle in Pennsylvania. I here he has rod kits pretty fair pricing too!
Stick with the 17 rear, they work well and IRC makes a great tire.
Assuming you are in the USA.

Thanks for the replies, I'm investigating a few options before dropping $350 on the rod kit. Lets move on to 40MM forks. I have a decent set, complete with triples, but no axle. Researching prior posts tells me travel and length of the 40MM forks will be a problem on the '78WR.

Am I correct that the solution to length and travel is to use the damping rods from the 35MM forks?

If I use the 35MM damping rods, do I need to run the same length and diameter springs that I would have used in the 35MM forks?

I think you will find the damper rods from the 35mm forks will be too small in the diameter. I am sure it's the 40mm WR rods you need.