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Old 06-23-2014, 09:12 PM   #1
PhatPhreddy OP
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Joined: Jan 2014
Location: N Thailand
Oddometer: 2
The Mystery of the 5mm Shims !!

I recently purchased a 2005 CRF450R in Thailand. One issue we face with bikes that have had Thai owners is the way they will bodge and modify anything instead of spending the money on importing correct parts, combine that with incompetent mechanics makes any bike owned or worked on here a bit of a crap shoot. This bike appears to have come into the country only 2 years ago and was hopeful it hasnt reached terminal stages of modifications !!

The bike had (presumed blown) been worked on and claimed new top end, barrel, head, valves etc.. With all new imported parts. The bike is incredibly hard to start, even push starting it needs to be pulled up to 20 kph or so, 2 of us pushing it failed, but once it fires that way it starts and runs ok. Hot cold whatever is irrelevant I just cant seem to kick it to life. When running it is possibly a teeny bit rattly (valvey) but I dont have a lot of 4 stroke MX experience to compare to. It may be my lack or comparative MX bike experience. I was going to pass on the bike but made an insulting lowball offer that even if I had to import a new engine would still work for me, and it was reluctantly taken. Now need to go through the bike to get it back to where it should be. I basically expect to find mysteries and the task is to get the bike to stock and usability with the lowest cost and workload. Basically I took a flyer on rolling the dice on it.

Early hopes that the fact it was a horrible condition and incorrect spec spark plug, didnt get it kicking..

I havent pulled the head, and it appears to be new head barrel and valves as stated. I dont want to pull it yet if I can avoid it in this round. First to deal with what I can see here. Its my plan, that once these valves wear to swap out for steel / kibblewhite valves and springs for more day to day use and lower maintenance schedules.

The valves were not shimmed properly both inlets were 0.45 with 2.4 / 2.45 shims.. Thats looks like it makes sense (even if the gap is wrong) with shims right out at max sizes and to shrink over the life of the valves.

The outlet valves however are crazy.. one is .30 with what I think is a 5.0 shim and the other is 0.15 with a shim thats 5.20 !! These shims also possibly look a little home fabricated, very hard to be sure on this but appear so.

Also to note is they have cracked and welded (looks solid but still not what I want) the camshaft holder which will be getting replaced.

The camshaft has a marking on one area between one of the lobes as a HCDF No 24. This appears to be a stage 2 hotcam. The camshaft looks clean and even possibly new. There is no reason to suspect the cam to be worn or damaged.. While I understand in the west someone can have camshafts reground and re-profiled, thats not going to be done here in Thailand, at least not as cleanly as this appears, and the cost of sending it out of Thailand, to be reground, would exceed buying and importing another, which is why everything is modified here to save costs. In short I highly doubt the cam has been reground, which is the only thing I can think of to explain this...

So what can lead to this huge shim gap ??

If I follow the chain of parts from cam, theres the roller on the rocker arm, the rocker arm itself.. they all look clean, unmolested, and I cant see any reason or logic why they could be modified.

Without wanting to ask a dumb question, theres no way a hotcam kit comes with super massive shims is there ?? To somehow compensate for a lower 'lift' in the cam lobe ??

I want to get this back to clean unmolested, but I am a bit baffled as to where to start here. I cant see what is obviously wrong to lead to this situation.

Anyone got any ideas or suggestions ??

All I am left with is the idea that they may have used shorter valves ?? Given they had to buy and import all the other parts that doesnt seem logical they would do this. Parts not to hand would logically be 'adapted' but if doing a top end rebuild you would think valves would have been in the shopping list.. Also theres evidence that the (possibly homemade) shims have been used on both sides. meaning they may have been in there, prior to its latest rebuild ??

Sorry for long post.. But baffled as to whats happening here.
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