HELP!!!! New motor issues.. Need advice.

[bigH]

I have an 05 450. Just had the motor rebuilt. The only differences made in the motor were 13 to 1 piston and I had the head ported. Same exhaust and same cam that was used prior to rebuild. The motor does not want to start. There is alot of back firing. The motor has absolutely no bottom end. I have tried different jetting, swapping carburators (both carbs ran perfect on my practice bike). When I was swapping out carbs I noticed alot of raw fuel in the intake and the intake boot. I actually had the air filter off and raw fuel was blowing into the air-box. I am stumped...

[flyboy1294]

Sounds like either timing or valve lash is out of spec.

[DnB_racing]

ya im guessing a timing issue,or a valve clearance or sticking problem,

after porting did you clean the ports VERY VERY good with a parts washer and compressed air?not all porters do this, its something you should always do
the filings can destroy the seals and coating on the valves,and your new motor


as long as the head wasn't decked or you used a crf head gasket, the timing marks will line up,
if you did have it decked or crf gasket , you would need to dial it in with a degree wheel, as this will change timing


Its also not a bad idea any time you change pistons or head to do a squish test to be sure of piston valve clearance

[400exrider707]

I would double and triple check the timing on it.

Ironically enough, I had this exact thing happen on my KLX after a high compression piston and ported head (just coincidence), but I got it on, fired it up, rode it for maybe a couple minutes and then started experiencing about 1/2 power and it was terribly hard to start. At WOT it would only run about 1/3-1/2 of the normal RPM's. Pulled it apart and found the timing key sheared...

[bigH]

I want to send out a HUGE thank you to Brian @ WPP. He figured out the issue with my new motor that was built by someone else. Yes, the cam was retarded. Brian took the time out of his very busy schedule to look at my engine. Again, thank you Brian for all your help, quick diagnosis and repair.

[wppracing]

Glad to help. Now you guys can finish the suspension upgrade and ride this weekend.

[400exrip]

If it was out of timing just a little bit it would have probably bent the valves.

One time I was putting together one of my motors and had the timing just a hair off, and tore the motor back apart to find
2 brand new bent kibblewhite black diamond intake valves, luckily I had 2 more on back up.