New Port and Polished head, Quad only starts cold. (TRX450r)

[karatekid14]

Okay, here's the deal. I have a 2007 electric start TRX450. I have an HMF pipe, Stage 2 Hotcam, No air box lid. It was jetted for it and ran great. Always adjusted my vavles every few months, cleaned my air filter regularly, quad ran like a clock.

I bought a brand new head from Honda, got it ported and polished, got KibbleWhite Valves and their HD double springs put in it. I bolted it on and this quad screams. But.....

PROBLEM: It only starts up cold... if I drive it around for 30 minutes and try to start it again, I'll kill the battery before it fires. If I wait for it to cool down it'll fire right up then. When it's on and running, it runs good. I know most of you guys are going to tell me it's the valves but I've checked them three times. They don't move. And it sometimes will hick-up. Like I'll be giving it consistant throttle and it'll skip, like I have water in the fuel or something.

On a side question with the valves, should I be still using stock clearance measurments with this engine work, since it's not exactly stock? I'm using .16mm for the intake and .28mm for the exhaust.

So next thing I was thinking was the jetting. It's ported, so more air, my fuel to air ration must be off. So I pulled the plug, it is a light tan, maybe too light tan... It should be a dark tan / light brown color right? Here's my jet sizes: 165 main jet, 48 pilot jet (long flat head jet) and 75 on the other jet (one that looks like a stubby flat head screw).

Any suggestions guys? Anyone have this problem before and knows the fix?

[mx Eli]

I have an 04 with a hmf system and hrc cam with no air box lid and I run a 170 main jet if that helps

[karatekid14]

Na, that doesn't really help the 04-05's are different carborator and different jets than the 06-08's. The carb on yours is a 40mm, mine is a 43mm. The jet sizes will be off. But thanks anyway.

[mx Eli]

the 04 and 05's have a 39mm regular carb and the 06+ have a 41mm flate side

sorry i didn't see the year

[kenny450er]

im runing the same set up you are and have the same problem im running 170 main jet an a 50 piolt jet 2.5 turns out with the fuel mixture mine will start hot but takes a few cranks and gets alittle stubern most the time i just let it sit 10 min an fires right up.

[witech]

A hard hot start first 2 things to look at are tight valves and a coil that gets weak with heat.

[kenny450er]

Originally posted by witech
A hard hot start first 2 things to look at are tight valves and a coil that gets weak with heat. i run my valves a touch on the loose side. when the coil gets hot is their a spec to check the resistance or just replace it an see if the problem is fixed and if so are their any after market high output coils.

[witech]

Actually just run it and heat it up. When the quad doesnt start pop the spark plug out and see if its sparking like it does cold. That would be a good time to do a quick hot compresion check to see if your valves have sunk into the seat. Do you have titanium valves yet?

[kenny450er]

all new ss kw valves new dual rate kw springs and seats were cut valve lash is good compression is good

[witech]

After reading the first post again the hiccup leads me to think it may be an ignition problem. How is the spark when its hot and not starting?

[karatekid14]

I've also been told about the ignition. I'm running a Big Guns over Rev box. I've been told to get rid of it, that they're not that good. I still have the stock CDI box, I'm going to plug that in and see how it works. I have my quad completely dis-assembled for powder coating and overhauling. I'll have to wait until I get it all back together before I can trouble shoot the engine problems. I'll post what I find out. But what I'm going to do is change the jets, put the stock CDI box back in and check the timing chain and decompression arm. I'm positive I've checked them when I put the head on and they were good but stupid mistakes happen. I hope it's not the coil.

[aDviSol2y]

Do one thing at a time.

[tayyo789]

your jetting isnt the problem. A lot of guys I know that have 450r's had this problem and it ended up being their intake valves.

[hendershot106]

Sounds like a valve problem first, and secondly possibly an electric problem...

1. valve lash, if not it..
2. Coil or CDI
3. Stator

[karatekid14]

Guys I know you're thinking the valves, and that's the first thing I thought too. I just put brand new KibbleWhite Stainless Steel valves in the new ported and polished head along with double rated KibbleWhite springs. I had the valve seats cut to seat the new valves perfectly. After taking it out for the first time I thought it was the valves too the night that I put it all together and rode it and dicovered the problem but I checked them three times and the clearances do not move. They are dead on every time.

I bought a new dynatek ignition coil for it on ebay. And I'm putting the stock CDI box back on, I'm going to use the HRC (Honda Racing Company) plug in harness with it to boost up the power in order to replace my big guns over rev box.

Ever heard of Valpor Lock?

I found this info online: Hot starting problems are usually fuel related. When a hot engine is shut off, the temperature of the engine and everything on it continues to rise for awhile as the engine undergoes a period of "heat soak." This can cause fuel to boil inside the carburetor bowl, fuel lines and fuel filter. When you attempt to restart the engine, "vapor lock" obstructs the flow of fuel and the engine doesn't want to start.

What do you think? It sounds like it's what's happening to me.

[tayyo789]

Do you have a hot start lever?
I was talking to my dyno guy and he told me he's had countless guys on 450r's that cant get their bikes to start when they're hot. I was having the same problem on my hybrid until I put a hot start on it. If I were you I would go run it, get it hot. Get it to where you're having this problem, and then try to pull start it. If it starts, then its not vapor lock.

[EXKid416]

Run OEM valve clearances since it's liquid cooled. Instead of relying on the valve clearances to say wether your valves are sealing right, do a cylinder leakage check. It's possible you have an electrical problem, you'd pretty much need to do peak voltage checks of your stator and pick up coils when cold then when the problem exists. Are you certain that you do not have a fuel system 'problem'? A few things to think of, idle speed is 1700+/-100rpms, make sure its plenty high. Check for intake air leaks, also.
Have you tried starting fluid when its acting up? If that doesnt light then its probably a electrical or mechanical problem.

> I have seen cam sprocket mounts twist on the cam, usually those machines over heated or the sprocket bolts came out and twisted it, but still worth checking