05 CRF450X diagnosis hell

Problem, Bike starts terrible, once running it runs ok, but backfires when you let off throttle. Electric start, forget about it. 30 kicks, not unusual.

History, Bike new, runs start great. Trailer to race 6 hours away, runs like crap, had to run choke whole race. (still finished 5th in :thumbsup:. Took it to local Honda dealer because I was off to Colorado in weeks. They say they have it running great. Wrong. Runs the same or worse.

On a picnic table in Colorado a friends starts to disassemble my carb only to find no air screw.

Buy air screw and bike runs much better, but has got consistantly worse at starting and running and better at backfiring. Have spent over $500.00 at honda shop and it is no better.

Shoot either in carb, starts at any time. I feel it is then in the carb. What say you.

I know this is thumper talk but I came from a CR250 that was a one kicker, it is looking better and better.

Very frustrated and need a base line to start from.

Go back and set everything back to factory specs. New plug, filter, etc. Check your valves while you're at it. It's most likely in the carb, but at the same time you want to rule out other issues that could be imitating a jetting problem. The valves could be tight, causing the backfiring or it could be running lean.

Start fresh and work on one thing at a time. When I have a problem and I'm trying to diagnose it, I always have a specific order I go through.

1. Wash bike

2. Fresh filter

3. New spark plug

4. If carb problem, I check all settings and write down, then set back to spec.

Good Luck!! :thumbsup:

Steve

clogged fuel line, clogged fuel filter in petcock, clogged jet in carb, running 87 octane, air leak somewhere causing it to run lean, timing is messed up, etc. :thumbsup:

I feel your pain. I ride a YZ250 and like the simplicity of the one kicker machine.

Ok, if you found that you had no fuel screw (fourstrokes don't have air screws), then you've been sucking dirty air in the carb??! That's when you stop riding, and start wrenching. Learn how, or there will be plenty more $500.00 invoices. I don't mean to be an ass, but this is not a street bike: you have to maintain it very often. Get a manual, and a friend with some experience, and go at it.

Your probably have a filthy carb!

- clogged pilot jet; clean and verify by holding up to bright light

- clogged pilot passage: lots of 80ps air/carb spray and no sharp objects

- air cleaner not seated properly, or edge not greased, sucking in dirty air

- Accelerator pump cover is not seated/ is leaking

- loose carb boots sucking in dirty air

- bad gas

I would also check the float system in the carb the new gas additives have been making the valve stick up in here in the east.Plus I would say NEVER use starting fluid on anything you like.It is a Honda if it does not start in a few cranks somethings wrong!!!!!I say clean the carb real well and see what happens.Read your owners manual running the bike with the carb on is real bad for piston/cylinder ware.

Take the carb off and take it all apart. There's dirt in it somewhere.

This has all the making of a dirty carb. you could tweak here and there and never get anywhere. I agree take it apart.

I would also check the float system in the carb the new gas additives have been making the valve stick up in here in the east.Plus I would say NEVER use starting fluid on anything you like.It is a Honda if it does not start in a few cranks somethings wrong!!!!!I say clean the carb real well and see what happens.Read your owners manual running the bike with the carb on is real bad for piston/cylinder ware.

+1 on the stuck float, had a similar problem, but not back firing, nd it was the float, drove me mad as I tore it apart multiple times to clean jets but nothing until I though hmm tap that black thing when fuel is running into it.

How about a clogged or kinked gas tank (gas cap) breather tube?

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