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Discussion Starter · #1 ·
I'm just curious how the CRF cam chain in the TRX400EX engine is working out for the guys that have done it.

I don't quite believe it is as good a conversion as everyone seems to think it is.

Physical characteristics: TRX400 cam chain weighs 6.2 ounces CRF chain weighs 7.9 ounces - TRX chain is designed to fit a sprocket 4.75mm wide, the CRF chain is for a sprocket 6.55mm wide - the CRF cam chain guide is 11.2mm wide between the flanges, the TRX guide is 9.5mm wide - the TRX chain is 6.85mm wide and the CRF chain is 8.95mm wide

The CRF chain is designed to make a tighter circle (17 teeth on the crankshaft and 34 teeth on the cam) while the TRX chain runs on 19 and 38 teeth. FACT: it takes more horsepower to bend a chain around a smaller diameter circle at high RPM than around a larger diameter circle.

The CRF chain running on the TRX guides will destroy the guides in a short time and start doing engine damage. I would liken it to running a 530 drive chain on the CRF's 520 sprockets. The 530 chain is heavier and wider, but it cost less than a 520 chain and it fits the sprockets. It won't go through the chain guide, so it has to be modified or eliminated. The chain will move from side to side on the narrow sprockets which causes contact with the engine cases and damages the case around the sprocket.

Let me know how the "upgrade" has worked out. Has it shortened the life of the tensioner or guide? Does it run quieter or make more noise? Do dyno runs indicate faster or slower acceleration and does the increased rotating mass reduce the maximum attainable RPM?

I have never performed this "upgrade", but I'm sure someday I will be asked about it and it's advantages or disadvantages. Therefore I am asking those that have done it for feedback about both short and long term experience.

Let me hear it!
 

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Well not to sound like a Negative Nancy type of guy but being a Mechanic I wouldn't see the reason to even swap over to a CRF Cam Chain. The TRX Cam Chain vs the CRF Cam Chain really not gonna notice a difference in Power or Longevity. "Maybe it will last longer?" because the CRF Cam Chains are meant for High RPM's and the 400EX's never will make those RPM's making it not as likely to stretch over the the stock chain... But I would just leave the Stock Cam Chain honestly. In my opinion it would be Unnecessary Labor and I have really never seen a 400EX Cam Chain wear out that fast unless it was a Hard Ran engine for 10+ Years. For Example I had a 02 Warrior "Now my friend Owns" and the first 4 years of its life was Street Legal "Always High RPM's" and still to this day no Cam Chain Slap or anything like that other then the Engine smokes a Little when it's cold only though and still is ridden allot.

Hope that was Good information for you.
 

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Discussion Starter · #3 ·
Thanks for your 2 cents - I am a mechanic and a shop owner

The TRX400EX uses the same cam chain as the XR400R - the chain's life is directly related to the kind of oil and the frequency of oil changes. My 99 400 has the original cam chain and at last check, the chain was fine. I raced this till 2004, sold it to a friend and he has raced it since. The motor has never been rebuilt or even had a clutch put in it, but it has had Silkolene 15W50 synthetic oli run in it and changed every third race since new.

In my opinion, there is only one reason for using a CRF chain - cost, but there are many reasons not to run the improper size chain.
 
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