valves

[QuadRacer18]

i have 1.65mm shims in my intake's. the quad got VERY hard to start over time and i thought i had clearance issues, so i went and got the biggest shims that are made, the 3.5mm and put them in. now the quad still wont start but every few kicks i get a VERY loud backfire. this means im getting enough gas and my intake valves ARE in fact opening, right.... let me know what you think.

Are your valve clearances correct?

[QuadRacer18]

my exhaust clearances are right on, but im doubting if i stuck the feeler guage in the right spot when going under the cam... you cant see and the fact that i only have straight feeler guages makes it harder. is there an easier way to see if spec's are correct?

[Chino886]

http://crfsonly.com/calculators/crf250-valve-shim-calc.php

[QuadRacer18]

now, either way... if the quad was pulled behind another quad and bumped, it would still start, right? Unless my valves are sucked up into my head... so is this correct? my buddy can try pulling me and if i cant get the bike to fire then i know i need new intake valves, springs etc. but if it does start then i just need to fine tune my clearances... right?????

If you never had a valve job and you have an 04 there is no doubt you need one. Order the Kibble White stainless steel valves and the rest Honda parts.

[jshtex]

As the head / valves wear they will sink into the head. Under normal circumstances you would end up going with smaller shims as they wear. So putting a great big one in would only be more likely to hold the valves open and keep it from running correctly.

At this point If I was you I would bite the bullet and get a professional to take a look at it.

Also starting it with that big a shim in there could be a bad thing. It could lead to piston to valve contact and $$$.

[Rulz]

Don't buy $hit until you get the correct feeler guages. Run to Sears and buy some longer, more flexible feeler guages and then measure your intakes and see what you got. Your intakes may be just fine.

The intake valves are tight. I would bet on it. They are so tight that the smallest shim won't even fit. I guarantee it.

[jshtex]

Originally posted by Rulz
Your intakes may be just fine.

You think so? With a 3.5mm shim in there? :)

[QuadRacer18]

alright guys, im gonna pull the head off and get the valves out and get all new parts... will i need to get any machine work done to my head or anything? or will i only have to get the seals, valves, keepers and springs? thanks!

You need to have a machine shop do a valve job on the head. It cost me $125. for the valve job and $65. for assembly of the head all shimmed and ready to bolt on. I did a piston and timing chain while I was in there. It cost total about $620 for parts and the machine work. I did all of the disassembly and assembly of the mototr myself. You will be very happy after it is done. Good luck

[jshtex]

Originally posted by QuadRacer18
alright guys, im gonna pull the head off and get the valves out and get all new parts... will i need to get any machine work done to my head or anything? or will i only have to get the seals, valves, keepers and springs? thanks!

The absolute first step is to check the valves correctly. It is possible that all you need is some shims. If you have already done that what were the results?

[trx450jason]

You can buy angled feeler gauges at sears which help so much with checking the exhaust vavles.

[d3ktrix]

Originally posted by trx450jason
You can buy angled feeler gauges at sears which help so much with checking the exhaust vavles.

I think u mean intake valves =)

[GIXXER1KR]

B4 u take the head off .. 1.get a Hotcams shim kit...2.. buy a nice digital caliper and some good quality angled feeler gauges!!!I got all Craftsmen,,a bit pricey but a nice investment down the road!!The cost is well worth it to do it right the 1st time instead of pricey repairs.And never tow a bike if it dont start..Especialy if it ran b4 u worked on it!!!I would look at whatever size intake valve shims u had and there origanly and cut it in half...EX. if u had a 3.0 try a 1.5 and turn the engine over by hand and recheck your intake clearances!!!I doubt it as bad as u think!!! I beat on my 06 for 1.5 years and 1 of my intakes were tight by .001 and one of my exhaust were loose by .002 and off a little on my decomp lever so if u maintaned your bike properly u may get by!!!Good luck and let us know how u make out!!!