HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
Nitrousman

Cleaned my carb, replaced jets, still only run with choke on

12 posts in this topic

Not sure what's wrong with this thing at this point. Occasional backfire while starting it, and it still only wants to idle with the choke on. I was able to ride it and once I got going it would run with the choke off but I had to keep the rpm's up or it would stall. pops quite a bit when coming off throttle while it's in gear. I blew out all the passages with compressed air and a full can of carb cleaner plus I replaced the jets. The choke button does not like to stay out now so I have to hold it with my hand while I start it. Are my valves screwed? This is the first 4 stroke bike I've owned and so far I really don't like it. The bike is in good shape but I can't figure out why it won't run right. It's a 2005 YZ 450F. I drained the tank when I had it off so it has fresh 93 octane gas in it now. Anything else it could be besides the valves? Thanks.

Share this post


Link to post
Share on other sites
Did you ever check your valve clearance?

That was going to be my next thing to check. I've not done any work on a 4 stroke motor before so this will be my first shot at doing the valve check. Do the instructions in the FAQ cover my 05 YZ 450F? It doesn't show my bike in the list of covered bikes. Anything I should watch out for when I'm checking them? Thanks.

Share this post


Link to post
Share on other sites

The procedure is the same, yes. The clearances for yours are listed in the manual as is the torque pattern for the cam saddle caps. While you're in there, check the cam timing before you take either cam out (if that becomes necessary).

If you just check them and find them OK, nothing further will be necessary, but if you have to adjust them, some important points are:

  1. There is a half circle locator ring on top of each ball bearing. Don't drop it down the chain tunnel.
  2. Reseat the caps BY HAND all the way against the head, using no more than a gentle tap or two with a screwdriver handle if necessary. DO NOT pull them down with the bolts if they resist. Figure out what the hold up is and fix it
  3. Never remove the chain tensioner unless the engine is in the timing postion (TDC on compression) and never rotate the engine more than 30 degrees in either direction with the tensioner slacked off.
  4. Don't turn the engine with either cam out unless you hold tension on the cam chain.
  5. Use care in torquing the caps. Use a good torque wrench, don't guess. Take them up in three steps to their final torque specs, and follow the pattern in the manual. The book calls for 86 in/lb. IMO, that's more than needed, and I normally us 75 in/lb instead.

Share this post


Link to post
Share on other sites

Thanks for the info, dealer seems to think I have a carb issue from what I've told the tech so it might be worth a $100 bucks to have them look at it and rebuild the carb again. They think I have some varnish somewhere in the carb but everything seemed pretty clean to me.

Share this post


Link to post
Share on other sites

I had the same problem. I ended up cleaning it again and again but every time I would get the same result. With old street bikes the adage is you usually have to clean them three times. Anyway, I ended up sending it to ZipTy for their clean and mod. Works quite well now for $125. For the extra 25 it is probably worth it.

Good luck,

Jim

Share this post


Link to post
Share on other sites

Did you have the slide out of your carb and if so did you reinstall correctly?

Share this post


Link to post
Share on other sites
Did you have the slide out of your carb and if so did you reinstall correctly?

No I didn't remove the slide but it ran like this before I even removed the carb.

Share this post


Link to post
Share on other sites

You really need to check your valve clearance and your cam timing. If there are issues with either one of these, nothing you will do to the carb will make a difference.

Share this post


Link to post
Share on other sites
You really need to check your valve clearance and your cam timing. If there are issues with either one of these, nothing you will do to the carb will make a difference.

After I put the carb back together again if it doesn't run right I might just let the dealer figure out for $100 bucks. These are the times I miss a 2 stroke.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0