Rebuild Engine top end

[416rider]

:devil: Do you have to rebuild the top end every 30 hours?:devil:

Originally posted by 416rider
:devil: Do you have to rebuild the top end every 30 hours?:devil: that is what my dealer told me but I have like 10 hours on mine & mine is fine

[lukester720]

No! That is for the crf dirtbike, tell you dealer to do his homework and to stop trying to steal your money. The trx was given an extra piston ring to prevent this type of ongoing maintence.;)

[KYmxracer52]

I was told by a mechanic that the valves are the weakness of the 450 motor. He said his CRF450 was like this, but he didn't know about the atv's. He said on the bikes the valves will get stuck in the head if you don't adjust them at least once a month (and that's riding once a weekend). He said if you put steel valves in them, it will cure the problem. Anyone heard of this with the new 450R's?

[ZRider400]

Originally posted by KYmxracer52
I was told by a mechanic that the valves are the weakness of the 450 motor. He said his CRF450 was like this, but he didn't know about the atv's. He said on the bikes the valves will get stuck in the head if you don't adjust them at least once a month (and that's riding once a weekend). He said if you put steel valves in them, it will cure the problem. Anyone heard of this with the new 450R's?

450r's come with steel valves..... not titanium like the bike.

sound sto me like this dirtbike is really high maintenance :eek2:

[KYmxracer52]

That's a relief about the valves!! Yeah, I'd thought about getting a custom CRF450 in an aftermarket 250R frame to race. After hearing about how high maintenance the bike motors are, it just makes me want a TRX that much more.

[rowlrag]

I'll try and simplify this,, RIDE IT TILL IT DIES:D and don't think about it till it does;)

[BIGBLOCKBILL]

I just tore mine down tonight to put the FST 500 kit in. Everything looked good even after roughly 75hrs of use. Hope the 500 wears as well.:D

[rowlrag]

What all is in there kit Bill? you send them the cylinder?

[BIGBLOCKBILL]

You get piston (12:1),rings,gaskets,cam and exchange your cylinder. Mike Benson has the same set-up and I can say first hand it runs very well. Haven't ridden it but he sure pulled on me in the straights at the Wisp.:o

[rowlrag]

Yeah, it's pretty mean:grr:

[BIGBLOCKBILL]

I see you run 4 st A, how did you make out at the Penton?

[redrider05]

Originally posted by lukester720
No! That is for the crf dirtbike, tell you dealer to do his homework and to stop trying to steal your money. The trx was given an extra piston ring to prevent this type of ongoing maintence.;)

Just to let you guys know you are suppose to change the dirtbike top end every 10-12 hours

[rowlrag]

Originally posted by BIGBLOCKBILL
I see you run 4 st A, how did you make out at the Penton?
Led from the start till the end of the 3rd lap when a bottleneck became involved, and trail was rerouted behind us with no invitations to take it. So sat there and got lapped, first to 7th.

Originally posted by redrider05
Just to let you guys know you are suppose to change the dirtbike top end every 10-12 hours wtf is that sh*t? man thats crazy!

[Spikers400]

WOW. I have a crf, and i probably have 30 hours on it. I am yet to replace the piston and rings. I have checked the vavles a few times, they were always righton. Do you guys think i should throw a new piston in it?? Even if its running good, so far it has been trouble free. Then again i dont race, so im not running it wide open constantly. I think they want a new piston and rings every 10 hours under race conditions.

[lukester720]

IMO those numbers are just set up for the people who race, if its not getting excessive noise or smoke I wouldn't be too concerned.

[Hbobb]

Originally posted by Jumbo747
sound sto me like this dirtbike is really high maintenance :eek2:

I had to reshim the valves in my CRF about 1 month (20 hrs) after I got it. Took about 20 minutes and cost $10. I then rode the bike for two years checking the valves periodically. Never had to do anything except clean the air filter and change the oil and filter. Just recently, with over 250 hours on the engine, my intake valve clearance went to zero. This is what happens when the hard coating on the titanium intake valves goes. I am now putting in new stock titanium valves, springs, and stem seals. Even though the piston still looks new, I am putting in the 04' piston as well. Not really that bad for a high performance racing engine. Two years of hard riding and almost zero maintanace required.

I opted to go with the stock valves rather than installing the stainless steel valves that are popular. I was concerned over the stress added by going with a heavier valve train. I also like the fact that the titanium valves go without damaging the head. If I had stainless steel valves, the next time might be valve and head replacement. If anyone ever does put SS valves in the CRF motor, they must make sure and put heavier duty valve springs in also.

thanks alot Hbobb...just learned alot from that post..

[Spikers400]

Yea me too, thanks. I was also wondering, if i have been riding it so far with no problems, does that mean my valves will hold up? Or does it mean that indefinatly my intakes will eventually drop through? Would it be best to wait till they gone or do it now? And how much work is it to put valves in? Ive never had to do it, can you just throw them in? Thanks for the help,
Ryan

[Hbobb]

The valves will not last forever no matter what. Read your manual carefully and check the valve clearance once every month or two depending on how much and hard you ride. No need to replace the valves until its time. Often, it will get harder to start when the intake valve clearance gets very small. 0.006" is specified clearance on the intakes. Just keep checking and shim as needed. When you can't buy any thicker shims it is time to replace. Don't ignore this maintanance or you could end up needing a head, cylinder, piston, or maybe even rod. The exhaust valves usually are no problem. I'm not sure how long those will last...probably many years.

The CRF/TRX engine is very easy to work on. Unless you are a very experienced expert engine mech, I would buy the service manual from Honda. Valves are easy to replace if you have a spring compressor or can figure out a way to make one. I am too busy right now and am paying my local dealer $200 to do it all.

im going to pay my dealer $125 to do a break in check up & adjust vlaves & make sure everything is going good in there. I also get a free ATV wash..

[Spikers400]

Thanks, i think im going to get a manual. I have some expierence with engines. I did my ex, but i have no experience with valves. THanks for that information.