cranky

[rockyroad]

Well I'm the first to post here and doing first bottom end. Thanks to Jeff and GasGas riders for the help. Left crank bearing appears to have inner race stuck on crank, and how is the outer race removed from case, as it cannot be pressed. I assume heat is the answer for both, but specifics would be great, as I don't know how to "pull" the race from the case/crank. Bike is '01 xc250.
Thanks.

 

[roostafish]

Happy to report, I've done this lots of times, and you'll be very pleased at how easy it is. Put that left case half in the oven (make sure you wash the heck out of it first so your wife doesn't kill you for the smell) It will need to reach 300 degrees of surface temperature, so crank the heat to about 310 degrees F. Leave it in there 'till you hear the race fall out. The aluminum expands quicker than the steel, and it should fall right out. Too bad the whole bearing wasn't still in there, 'cause the weight helps it fall out, but it should work anyway. It may take an hour to heat the case up that much, so don't worry about getting up tight about it not falling out after 15 minutes. You'd be well served to check the temp of the case with an infrared thermometer if you have one available, you'd be amazed at how long it takes to get that surface temperature up.

 

[rockyroad]

Thanks! Do I need to worry about the other bearings while heating? Any idea about the race that's on the crank?

 

[webmaster]

Rocky,
I asked Les @ lt-racing what he would do. He spent time as a machinist at Boeing and also is a Honda Factory Trained Tech...

If the race on the crank does not come off easily - you will need a bearing splitter and a hydraulic press to do the job. If you don't have practice at using either of these items to perform this task - the suggestion is to take it to a machine shop that does and have them "deal with it" for you...

Heat (torch) should be used as a last resort if bearing splitter and press fail to do the job. "You don't want to heat up the crank like that if you don't have to..."

Jeff

 

[rockyroad]

Thanks for the reply. Appreciate your contacting Les, I'm surprised of his concern with the heat. I was going to place crank next to the ice cream for a few hours then carefully heat race with the propane "torch". If too much of a risk I will do what you suggest.
Thanks again.

 

[GMP]

Jeff's suggestion is best. The bearing splitter/puller in fairly common, and if you have access to a press it would not be too difficult. A little heat ON THE RACE ONLY may make it eaiser. If you look in the GG manual, they referance a tool that you heat separately, and then clamp on the race to expand it. I have never used this, but have rebuilt a couple automotive manual transmissions that had many press fits with the press/puller method. Another option is to VERY CAREFULLY grind slots in the race on each side, as deep as possible without hitting the crank, and then hitting it with a punch to split the race in half. Its hardend and brittle.

Have the crank rebuilt and balanced, don't do the job halfway. Changes are the crank shop can eaisly remove the race and save you the trouble. For installation, get some dry ice and freeze the crank(I use liquid nitrogen because I have it available but this is not possible for most people). Before you do this, lube the rod bearing, and warm the assembly when complete to drive off the condensation that WILL form from the intense cold. Heat the race and it will just about fall on, but be quick.

For the case, roostafish has a great idea, it works well. While the case is still hot, drop in the new bearings(pre frozen).

This is how I do motors, as little force as possible.

Good Luck!

 

[rockyroad]

Thanks Glenn, any idea where to send for rebuild? And can anyone confirm the '01 CR250 rod is the one I want?

 

[webmaster]

RB-Designs.

www.rb-designs.com

I have only let one person touch anything on my bike for the last 20 years - and thats Les. But, based on what I have seen, this guy gets added to my very short list.

Someone signed up with a login named of RBD a couple of days ago and I pinged him to see if he was "rb-designs" and he is...

I asked if I could write something up so that folks knew more about him and his work. . He lives very near me, so I will be writing up an article detailing his machine work and services available for gasgas owners. His "head mod" to optimize the squish band has had very good reviews.

jeff

 

[webmaster]

RBD,
Can you provide some detail on your costs and turn-around time for your crank re-building service?

thanks,
jeff

 

[GMP]

Ron at RB Designs is not eaisly reached by phone, but he is prompt in returning email. My head was the first GasGas he did, and it was flawless. Excellent quality and fast turnaround. If you want to do a head mod he is the guy.

 

[jeffd]

Hi Rocky,
I pinged Ron @ RB-Designs via e-mail. He responded he was busy with family in town this weekend and said he would reply back when he got a chance.

He did say he didn't know about getting parts needed and that you might need to dig these up, but it won't be an issue. I asked Les about it and he told me that GasGas uses a Vesrah Rod - same as an '81-'01 CR250. Ron shouldn't have any trouble to round it up for you. For reference, the Vesrah part number is VA-5001. I'll pass this info back to Ron.

jeff

 

[rockyroad]

Thanks for all the responses. Yesterday I sent the crank to Surf + Turf in Pomfret CT. I requested a Honda rod, they use Pro-X. From our conversation, they sound like a good company and the name reminds me of last night's dinner. Cylinder is going for a replate, most likely Powerseal unless someone suggests otherwise.

 

[RBD]

Hi rockyroad and others,

Just wanted to let you all know that I can rebuild these crankshafts and have been rebuilding all types of press together cranks for over 30 years now.

I design all of my own fixtures and tooling for Crank Rebuilding. I rebuild crankshafts from the basic 50 cc two stroke single cylinder to the 1100 cc four cylinder four strokes.

By the way rockyroad, the Pro-X rod kit is a great choice

Thank you,
Ron

 

[gasgasman]

Ron.
Do you balance cranks also?

 

[RBD]

Ron.
Do you balance cranks also?

No I do not do any balancing on most any two stroke crankshaft. I find that the factoy counter weighting of their cranks seem to be nutral.

When you start changing the balance factor you are making the engine more RPM specific. In other words, you can make the engine vibration smoother at a specific RPM range (not a very wide range at that). This will make the engine vibrate in other RPM ranges.

If you are building a road racing engine you have a narrow power band and it is usually at a higher RPM's. Balancing an engine for these higher RPM's helps both power delievery and reduces the vibration. It will shake at lower RPM's, but you are not running the bike at these rev's anyway.

Like I said, most factory singles are balanced for the all around power RPM delievery.

Ron