07 CRF450r top end rebuild

[mw878]

I am the original owner of this bike and I think it is time for a piston replacement. I have a lot of hrs from racing to desert riding. What all needs to be replaced? I'm pretty good about maintenance on the bike but have only had to adjust the valves once, just checked them and they are still spot on. Can just the piston/rings be replaced without doing new valves?

[Qqqqqqqqqqqq]

Yes , you can do that , you just need to keep checking the clearances . Watching for any sign of movement .

Fit a new cam chain and tensioner , I prefer the MCCT .

[adam8781]

yes its fine.  As a precaution i would replce the cam chain. And you also have an opportunity too add some hp, switch to a forged 13.5:1 compression piston. It is pump fuel safe and will give you a good boost in power.

[mw878]

Yes , you can do that , you just need to keep checking the clearances . Watching for any sign of movement .

Fit a new cam chain and tensioner , I prefer the MCCT .

Not sure what the MCCT chain tensioner is, I'm asuming aftermarket?

yes its fine. As a precaution i would replce the cam chain. And you also have an opportunity too add some hp, switch to a forged 13.5:1 compression piston. It is pump fuel safe and will give you a good boost in power.

Anything else have to be done for this piston or will it drop right in?

Thanks for the input guys, anything else I might need other than gasket kit?

[mw878]

I should ask what other things I should look for to point toward it needing a top end? Obviously the hours on motor and year. I rebuild my sons KLX110 a couple years ago cause smoke was coming out of exhaust which meant rings were bad, would this be the same for my 450 cause no smoke is coming out. I am having an issue with oil in airbox though.

[JJRace]

mcct - manual cam chain tensioner

 

biggest thing is to watch the valves.  once they start moving, time to replace/rebuild the head. 

[mw878]

Took motor apart tonight, checked valves and they are perfect. The cylinder wall looked really good, just some marks on the front and back of the cylinder. I have been reading up on honing and it seems most agree on reassembling with no oil. I thought I read somewhere that I could use a wire brush that is used for cleaning copper fitting to do the honing. I could just attach it to a drill and scrape the edges of the cylinder?

Parts that I am ordering:

Piston, ring, and clips

Cylinder gasket

Cylinder head gasket

Cam chain

Just in case seals are bad and letting oils mixI am also gonna replace:

Balancer seal

Crank seal

L/R case gaskets

I will also replace all seals for water pump.

Anything else I should consider?

[adam8781]

sounds like a good list. And yes the higher compression forged piston will drop right in no different than the stocker.

[mw878]

Sorry I keep throwing all these questions at different times but just posting them up as they come to mind. Any suggestions on how to clean the carbon buildup on the cylinder head?

[mx4life320]

THanks for the answers here.. I am gonna be rebuilding my 08 CRF 450. I dont know what to look for in the valves. How do I know if i will need to replace them.. The exhaust are spot on, only adjusted once. The Intakes are a little tight.  The compression seems a little low thats why I think it needs a top end. 

Can anyone help? 

[mw878]

THanks for the answers here.. I am gonna be rebuilding my 08 CRF 450. I dont know what to look for in the valves. How do I know if i will need to replace them.. The exhaust are spot on, only adjusted once. The Intakes are a little tight.  The compression seems a little low thats why I think it needs a top end. 

Can anyone help?

Can't help you there but I was looking into replacing my valves a few years ago and the shop asked me how many times I had adjusted them(which was once). He then told me don't both and call him when I can't adjust them anymore.

[mw878]

Well got my bike all put back together. I used all OEM parts and took cylinder down to my local Honda dealer, they honed it for $15. I used a wire brush on a drill to clean cylinder head and it turned out great. I am very confident in my timing being set, I double checked my valves and had to adjust one intake valve. When installing new OEM piston I put the rings in fresh oil before installing them on the piston and putting cylinder over it.

My problem is I can get it to start. What could I be missing? Spark plug is installed and all wires are plugged in.

[mw878]

Got the bike to start and it idles fine. Two things I noticed is I got a little drip from water pump weep hole, got like a tea spoon or so then it stopped. I only let it idle in my garage and twisted the throttle a few times long enough for the fuel to drain out of carb, it got not enough for coolant to come out of overflow tube. Are both of these normal? Any suggestions on the best way to break new top end in?

[pomoco]

Took motor apart tonight, checked valves and they are perfect. The cylinder wall looked really good, just some marks on the front and back of the cylinder. I have been reading up on honing and it seems most agree on reassembling with no oil. I thought I read somewhere that I could use a wire brush that is used for cleaning copper fitting to do the honing. I could just attach it to a drill and scrape the edges of the cylinder?

Parts that I am ordering:

Piston, ring, and clips

Cylinder gasket

Cylinder head gasket

Cam chain

Just in case seals are bad and letting oils mixI am also gonna replace:

Balancer seal

Crank seal

L/R case gaskets

I will also replace all seals for water pump.

Anything else I should consider?

I must have missed the thread, but I would never install a dry piston. I have been working on engines for over 25 yrs.

[mw878]

I must have missed the thread, but I would never install a dry piston. I have been working on engines for over 25 yrs.

Wish I would have heard more of the pros/cons before I rebuilt. I guess it isn't completely dry as I did soak the rings. I did notice some smoke coming out exhaust after startup.

[tonkaman]

Aren't you worried about the bottom end of a 7 year old bike? Don't take me the wrong way, I'm actually curious

[mw878]

Aren't you worried about the bottom end of a 7 year old bike? Don't take me the wrong way, I'm actually curious

The only thing I was worried about was the bottom bearing on the connecting rod but it actually felt good, even talked to a tech and he said it was good. I was kinda worried after reading all the horror stories that my bike was going to be a mess doing the rebuild, they must have built the 07 stronger than the earlier models. I've only adjusted the valves once and they cleaned up real nice. The whole process was actually easier than I thought it would be and I don't have a shop manual.

[tonkaman]

I actually have an '07 in need of its first head and piston service that's why I was wondering. I just can't imagine after a few hundred hours the bottom end is still in good shape. I haven't disassembled mine yet to find out

[Qqqqqqqqqqqq]

I must have missed the thread, but I would never install a dry piston. I have been working on engines for over 25 yrs.

Yeah , we all have our ways , I install dry rings , oil the piston skirt and pin . No problem's in over 35 years .

[mw878]

I actually have an '07 in need of its first head and piston service that's why I was wondering. I just can't imagine after a few hundred hours the bottom end is still in good shape. I haven't disassembled mine yet to find out

I didn't have an hr meter so I don't know for sure how many hrs were on it but I'm the original owner and have ridden it a lot from desert, sand, track and racing. This was the first time I did a top end on it.