Bike has to be pull started and wont stay running ?? CRF450

[walshltr450]

Ok i have a 400ex hybrid with a crf450r in it 03..
I have to pull start it it wont start buy kicking..
And it runs like **** and if i let it idel it will make like a pop and shut off.. It also back fires when i let off the gas and just runs horrible over all now power really..

Plz let me know idk what it is..


Thanks
Tyler

[protraxrptr17]

Check your valve clearance. Valves are probably worn out.

[walshltr450]

Do i need a mike for this?
I dont do much motor work i was gonna have a freind do it but dont know what needs to be done..
And he said bring him the head its the exhaust valve but i figured id ask here first

[outacontrol]

i agree its valve related. My guess is your intake (titanium) valves are out of adjustment, too tight and one or both is being held open, not allowing the bike to build up compression therfore not starting, and when it does, thats why your getting the popping. My head is off my crf right now, cuz of the same issue, going with stainless steel valves to eliminate the fight!

[protraxrptr17]

Don't pull the head off. Just take off the top cover. You'll need a feeler gauge and a shim set.

[walshltr450]

Well i pulled the head off and had a guy a mechanic look at it and he said it was fine.. I probibly had a loose timing chain..
Well i got it back on but i caint find any timing marks to set it at time..
Theres the arrow on the case but the ballancer doesnt have any markings besides a round hole..
The timing sprocket has two little lines but idk what to set them at.
Im going to the dealer in the morning to get a manual to check and set the timing and im gonna tighten the chain and get a new plug and try this..

Any thoughts..
The head and plug look like that are bruning perfect..

[walshltr450]

ok i got it set at time im pretty sure but still does the same thing.
When i kick it it seems like it wonts to start but just caint..
And it still backfires will trying to start???
im thinking of just running it to a shop and having them fix it im just lost on what to do..

[protraxrptr17]

I'm almost certain the intake valves need adjusting. Get somebody good to set the valves for you.

[Rulz]

If your bike pull starts and will not kick start, that is almost always an indication your intakes, especially your left intake has closed to zero clearance!

Use this thread as a step by step guide to check your valves. It's off a CRF250R but it's basically the same anyway:

http://www.thumpertalk.com/forum/showthread.php?t=179775

[walshltr450]

Well i dropped it off at my mechanics hes gonna check the clearance and stuff..
He said it sounds like one of the valves are to tight and hes gonna set it at time..

THanks
evryone

[outacontrol]

hope you get it all squared away. im sure it just needed re-shimmed.

[walshltr450]

Well the kid i bought the motor from had just rebuilt the wholething.. Well he had all the valves to tight and thats why it was running like it was.. So 70 dollars and some shims and itll be perfect curtis says.. So ill have my motor back tomorrow thursday..
But tonight i went to the track with a couple freinds to watch them ride and got a new bike..
Its a 04 crf450ex like mine with fullbore plastics..
Its got a legacy frame houser lt a-arms axis all around and a viper swing arm.. i gotta change a few things but my motor better come back like this one because this one would eat mine alive..

Thanks everyone for the help figured id share my good fortune with everyone..

Tyler

[duneflyer1]

YA, its def. the valves. Mine were the same way. I put in Kibblewhites and never a problem since.

Congrats on the new ride!

[walshltr450]

Well after 2 trips to get shims we got ur done..
But i got it home and it started right up..
Now its trying to start really hard but just caint seem to get it..
im gonna try a new plug tomorrow and see if that helps..
But it ran good when it first started..

[TampaBoy813]

Originally posted by duneflyer1
YA, its def. the valves. Mine were the same way. I put in Kibblewhites and never a problem since.

Congrats on the new ride! same thing here...after I redid the valves it was 100% easy starting!

[duneflyer1]

Originally posted by walshltr450
Well after 2 trips to get shims we got ur done..
But i got it home and it started right up..
Now its trying to start really hard but just caint seem to get it..
im gonna try a new plug tomorrow and see if that helps..
But it ran good when it first started..

Once you start to shim the valves, its all over. They go out of adjustment quickly, although, it shouldnt be THAT quick. But you're gonna have to get some quality valves put in it.

[TampaBoy813]

Originally posted by duneflyer1
Once you start to shim the valves, its all over. They go out of adjustment quickly, although, it shouldnt be THAT quick. But you're gonna have to get some quality valves put in it. yep its the start of the end for your valves..you need to get and install the KB White SS Vales...if you are going to keep the quad.

[walshltr450]

Well the guy told me a new plug would fix it so i did that still nothing.. ran fine when i pulled it but i caint kick it over..
I also messed up the rear cam cover bolt so im gonna have to get a new cam carier.. GREAT.. Well i think im just going to find a new motor and put it in because this one seems hopless

[duneflyer1]

Originally posted by walshltr450
Well the guy told me a new plug would fix it so i did that still nothing.. ran fine when i pulled it but i caint kick it over..
I also messed up the rear cam cover bolt so im gonna have to get a new cam carier.. GREAT.. Well i think im just going to find a new motor and put it in because this one seems hopless

lol, no not hopelss. Really you just need a new set of valves, and your problem will be solved, honest.

[2muchquad]

Most people assume its just the crappy honda valves when the reality its only part of the problem.The solution is stiffer valve springs.Whats happening is the stock springs arent holding the valves against the cam allowing them to slam and bounce off the seats.SS valves will only be a bandaid,replace them with new valves and springs and you'll be set.Dont despair,all hope is not lost.;)