[Garon]

Hi All,

Thanks in advance for any light you can shed on this problem. I have a 2004 CRF250 that I have had since new. Oil regularly changed, valves adjusted regularly, jetted well, linkage grease, etc and it has been a terrific bike. It is used for casual woods / trail riding only.

A few months back, it became very difficult to kick through with the kick starter. The best way to describe it is it feels as if there is so much compression that I need to use all my strength to get the kick starter from the top to bottom.

At this same time, it became very difficult to start, especially when it was hot. I had to let it cool down, it started fine and i rode a while and then stopped.

Since I felt something was wrong, I had a mechanic peform the regularly scheduled valve adjustment (instead of me). He said the valves were off, made the necessary adjustment and changed the spark plug.

I got it home and got it started, but it was still very difficult to kick through. I went riding that weekend and it died while hot, and then it would not start again until cold.

I didn't check the valves since he just did it, but took the carburetor off and did a thorough carb cleaning. After reassembly, it started right up but still very difficult to kick through. I took it riding the following weekend and the same thing happened (stalled while it was hot, and then not possible to get it started again).

I pulled the cylinder head off yesterday and meausred the valve clearances. Both intake and exhaust are less than spec. Assuming the mechanic correctly adjusted them, how could they go tight with only two short rides?

Also, what do you think could be causing the heavy resistance on the kick starter? And near impossible to start when hot?

I am thinking they are related.

[lightflight]

Hi All,

Assuming the mechanic correctly adjusted them, how could they go tight with only two short rides?

Also, what do you think could be causing the heavy resistance on the kick starter? And near impossible to start when hot?

I am thinking they are related.

Once the valves start to go they can go rather quickly. A shim job most of the time will not last long at all maybe a couple few rides.

[Garon]

Thank you for the reply.

I normally ride 6-8 times a year, and adjust the valves before each riding season. I would be surprised if the valves needed adjustment after two short rides (15 minutes each).

If the valves were not adjusted correctly, would a symptom of this be more pressure required to kick through the starter?

[Garon]

When the valve start to go, does that mean it is time to replace the valves / springs or does that mean it is time to replace valves / springs AND piston?

The Kibblewhite valves / springs and Weisco piston were installed 4 years ago and the bike has about 30 engine hours since then (I do not ride too much).

If the valves were begining to go, wouldn't there be less compression making it easier to push down on the kick starter? Or do I have it backwards?

Sorry for my minimal knowledge, but I learn so much by asking questions and reading in this forum. So thank you in advance!

[staffy24]

Hi All,

Assuming the mechanic correctly adjusted them, how could they go tight with only two short rides?

Also, what do you think could be causing the heavy resistance on the kick starter? And near impossible to start when hot?

I am thinking they are related.

Once the valves start to go they can go rather quickly. A shim job most of the time will not last long at all maybe a couple few rides.

time for a valve job seats cotters valves cam chain and tentioner piston rings go for the kibble whites or even better just get a complete head ready to bolt on

[124]

Assuming the mechanic correctly adjusted them, how could they go tight with only two short rides?

Also, what do you think could be causing the heavy resistance on the kick starter? And near impossible to start when hot?

Garon,

I think you are misunderstanding the valve shimming process.

The valves clearances will stay in spec until the valves/head starts to wear. The valves and the valves seats start to "cup". It is a deteriorating process meaning that the wear in the end is worse than the beginning.

As it starts to wear (the beginning), your first shim will last quite awhile. Depending on how much you ride, it may last a year. As it wears further, the time in between shimming is reduced exponentially. We ("the internet experts" ) always recommend going no less than a 130 shim. You are razor thin on the edges of the valve and risking catastrophy. With shims this small, you're likely to only get hours (or less) of in spec valve clearances.

So to answer your question about shimming. Shimming is a temporary process to delay a regular service interval - replacing valves and seats.

Regarding the hard to kick. The decompressor system is automatic and uses an inertia weight. The weight is designed to swing out of the way (disabling the decompressor) at around 600RPM. Your problem is likely wear related normal with age and use. The actuating surfaces of the decompressor weight/pin wear causing the system to "hang" (hard to kick). Sometimes it will even cause weird symptoms where the lighter you push on the kickstarter, the easier it is to kick over (lessening the symptom so to speak). Try it...

[Garon]

Great diagnostic information. When the valves/springs are replaced, are the 'seats' replaced or is that just referring to a location of where the valve sits for the 2004 CRF250? I was unable to locate 'seats' in the parts section and thought maybe the valve head location was machined into the head to fit the valve nicely.

And it sound like these 'internet experts' know their stuff as much as any mechanic I have come across! Thanks again for taking the time to help this budding mechanic!

[124]

Great diagnostic information. When the valves/springs are replaced, are the 'seats' replaced or is that just referring to a location of where the valve sits for the 2004 CRF250? I was unable to locate 'seats' in the parts section and thought maybe the valve head location was machined into the head to fit the valve nicely.

And it sound like these 'internet experts' know their stuff as much as any mechanic I have come across! Thanks again for taking the time to help this budding mechanic!

Sorry for the delay, I've been out of town for the weekend.

The seats are integral to the head as an assembly. A shop can replace the seats separately but Honda will only sell you a head. It's basically cheaper and easier just to buy a new head anyway...

It is rare to have to replace the seat. When its time to service the valves, the seats are typically "cut" to return them to spec. The worn portions of the seat are ground to specific angles. This is a random picture I stole from the web (ignore the numbers). You can see the relationship between the valve and seat...

[Garon]

Thank you for the reply. I am learning more and more with each post and look forward to tearing into this bad boy.

My trusted mechanic who installed the Kibble White Valves / Springs and Wiseco Piston asked to take a look at the bike and see what he could determine before I give it a try. I felt obliged since he has always done a fine job and is very trustworthy.

I will definately post an update when I hear from him.

[Garon]

Hi All -

I wanted to follow up with the bike diagnosis. The mechanic said the right exhaust valve shim must not have 'sat correctly' because there was no valve clearance there. He measured and adjusted the valves and the results are:

1) It starts on 1st or 2nd kick (hot or cold engine)
2) It is no longer difficult to kick through since the combustion is being let out in the exhaust.

I will report if anything changes after my first long ride, but hopefully I still have some life in this engine before a major overhaul is necessary.

Thanks again to this website for all the info and support.

[Garon]

Hi All-

I just wanted to report after the first ride that everything seems fine. Hopefully is was nothing other than the problems mentioned. It has no unnecessary compression and seems to start right up.

[crfsonly]

excellent news!