I am taking my bike a part because it has no compression. Typical honda titanium valve problems. I want my bike to last as long as possible before I have to do this again. I am putting kibble white valves and a new piston. What other parts should i replace while i have the bike open. It has about 60 hrs of wide open desert riding on it. Cam chain tensioner, guides?, :ride: what are the most common problems that lead to this bike blowing up. Thanks
CRF 250 R 2005 Maintanance
- Thread starter jbhsurf
- Start date
If the valves are worn have the seats properly machined (preferably with carbide tooling) to the correct angles and widths and install the Kibblewhite valves along with the Kibblewhite dual springs kit.
If you replace your worn OEM valves with stainless and just lap the seats without machining them the stainless valves are unlikely to ever seal properly and you'll reduce the life of the new valves.
Setting the spring installed height is very important. If the installed height isn't correct you risk having too little seat and open pressure and won't be able to properly control the valve.
You can measure the installed height a number of different ways. One of the easiest ways to do it at home is to take a piece of .090 brazing rod or something similar and cut it to the exact installed height. The you can use it as a go/no go gauge.
The Kibblewhite spring kits have a very good diagram showing what and where you have to measure.
Most good performance shops will use a Rimac valve spring tester to verify each spring before assembling a cylinderhead. I've tested a LOT of valves springs and I've found Kibblewhites to be very consistent and true to spec. You should have no problems just setting the installed height and assembling it after a good valve job if you want to do it yourself.
While the head is apart it's important to check for wear on the exhaust valve guides. The high rocker ratio used on the exhaust causes the bottom third (nearest the valve) of the guide to wear. If the guides are worn the valves won't seal for long and you'll be replacing them in short order.
Replacing the tensioner is cheap insurance, the cam chain guides wear slowly but it's worth checking them while it's apart. The OEM cam chain is very good and will last a few season of hard racing.
If you replace your worn OEM valves with stainless and just lap the seats without machining them the stainless valves are unlikely to ever seal properly and you'll reduce the life of the new valves.
Setting the spring installed height is very important. If the installed height isn't correct you risk having too little seat and open pressure and won't be able to properly control the valve.
You can measure the installed height a number of different ways. One of the easiest ways to do it at home is to take a piece of .090 brazing rod or something similar and cut it to the exact installed height. The you can use it as a go/no go gauge.
The Kibblewhite spring kits have a very good diagram showing what and where you have to measure.
Most good performance shops will use a Rimac valve spring tester to verify each spring before assembling a cylinderhead. I've tested a LOT of valves springs and I've found Kibblewhites to be very consistent and true to spec. You should have no problems just setting the installed height and assembling it after a good valve job if you want to do it yourself.
While the head is apart it's important to check for wear on the exhaust valve guides. The high rocker ratio used on the exhaust causes the bottom third (nearest the valve) of the guide to wear. If the guides are worn the valves won't seal for long and you'll be replacing them in short order.
Replacing the tensioner is cheap insurance, the cam chain guides wear slowly but it's worth checking them while it's apart. The OEM cam chain is very good and will last a few season of hard racing.
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