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General Category >> Rubber Side Down! >> Carburetor doesn't seem to like heat!
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Message started by crash_tx on 05/26/10 at 11:52:01

Title: Carburetor doesn't seem to like heat!
Post by crash_tx on 05/26/10 at 11:52:01

Hey smart people! I have a buddy who is having a hell-of-a-time with his 2003 Savage.

Seems he gets a really bad hick-up in the mid range after the bike warms up a bit. When the bike is cold, it seems to perform well enough- even without the choke. But as soon as he has 30 minutes or so on the engine, it starts being grouchy again!

The poor guy has paid a shop a ton of money to try and fix it. They couldn't figure it out and eventually charged the poor dude for a BRAND NEW carburetor.

I talked him into installing a Raptor 660 Petcock just to be sure. He still claims there is a problem in the mid range.

He's bringing his Savage by this Sunday and I would like to try a couple things. I'm going to check his main jet size and see if removing the washer on the needle helps. I'll also check his idle adjustment and valve clearances just to be sure.

I've searched the forum pretty well for this issue, but wasn't able to dig anything up that corresponded to this problem.

Anyone ever ran up against something like this?

Title: Re: Carburetor doesn't seem to like heat!
Post by Chief Gunner on 05/26/10 at 12:44:58

Two thoughts:

1. Metal tends to expand and contract based on temperature. Might be worth checking for intake and exhaust leaks once engine is up in temperature and the program is occuring.
2. If it has an oil passage that is clogged you might have one area that is heating up more than the rest and causeing a leak.

Just my 2 cents from a chair.

Title: Re: Carburetor doesn't seem to like heat!
Post by Boule’tard on 05/26/10 at 12:51:51

Probably a moot point now, but you can always check if it's a petcock problem by running it on 'PRI' which is the same as the Raptor petcock 'ON' (gas available to the carb even if the engine is off). Of course changing to the Raptor is a good mod even if that wasn't the problem. I guess you already changed the petcock, so there's no possibility of crud in the tank, and it flows freely with the gas line disconnected.

Another good mod is to shave down that white spacer at the top of the needle to 1/2 of its thickness. That helps with the hot running when the bike has stock jets. I would do that instead of removing the washer. Search on here for "white spacer mod" for a how-to.

And yup it is getting hot here in Austin. ;) Say, does your shop also do frame straightening? I wiped out pretty good on my dirt bike the other day, and a new frame is $1100 :-/

Title: Re: Carburetor doesn't seem to like heat!
Post by crash_tx on 05/26/10 at 13:38:47

4548524B4253465543270 wrote:

Yeah... I think I'll head down to Lowe's and pick up some of those #4 washers and stack 'em one at a time until the carb settles down (hopefully!)

Also, checking for air leaks on the carb boot after warm-up would be an excellent idea!

Frame Bent: Well... I have a frame jig I use for fabricating my customs. I might be able to throw your frame on there and check with the laser. If it's only a minor bend, we could throw a ram or hydraulic jack on there and try to straighten her out. What model and year is it?

Title: Re: Carburetor doesn't seem to like heat!
Post by crash_tx on 05/26/10 at 13:40:02

4E4544484B4A584343485F2D0 wrote:

I definitely think the heat is effecting something! I'll let her warm up and spray some carb cleaner around the boot. We'll see what the RPM's do!

Title: Re: Carburetor doesn't seem to like heat!
Post by bill67 on 05/26/10 at 13:46:43

I think he running to rich in the mid range make the white spacer thicker.

Title: Re: Carburetor doesn't seem to like heat!
Post by Boule’tard on 05/26/10 at 14:41:30

7C796E717C6A7761180 wrote:

Frame Bent: Well... I have a frame jig I use for fabricating my customs. I might be able to throw your frame on there and check with the laser. If it's only a minor bend, we could throw a ram or hydraulic jack on there and try to straighten her out. What model and year is it?

2008 Honda CRF 230.. tubular steel frame. I may get with you though your website once I strip it down enough to see what the deal is.

I don't have any other ideas about the midrange stumble, except that it is a good excuse to do a full uncork/rejet. Lemonade out of lemons and so forth..

Title: Re: Carburetor doesn't seem to like heat!
Post by justin_o_guy2 on 05/27/10 at 02:01:50

swap carbs & see if your bike suffers

Title: Re: Carburetor doesn't seem to like heat!
Post by fascar228 on 05/27/10 at 02:29:43

Hi All,
I suspect the electrics..could be the plug/plug wire or the coil....I had a bike which was ok till it warmed up and then.....it missed and coughed...I took the bike inside the house switched off all lights and started the bike....lo and behold....i saw small sparks around the electrical system.....1st I changed the plug..no change...2nd i changed the wire....60% of the problem solved...lastly I replaced the coil....All was well after that....so please see the electrics before undoing the whole machine.......

Title: Re: Carburetor doesn't seem to like heat!
Post by LANCER on 05/27/10 at 02:41:22

It could be as Fascar suggested, the ignition system.
But as a matter of routine, always check for air leaks in the exhaust system and at the carb flange just to be safe.
Then check the pilot and main jets and needle.
The symptoms noted can be caused by a "too rich" mixture in the low and/or midrange.
It could be that someone removed the white spacer entirely and that can cause a rich midrange.
Of course, since it will start and run without choke then the low range is likely too rich as well.
All is fine until the engine warms up and then the over rich condition causes problems.

Title: Re: Carburetor doesn't seem to like heat!
Post by crash_tx on 05/27/10 at 07:53:28

7479767B7D6A2A2F180 wrote:

He's bringing the bike by the shop on Sunday. I'll definitely take a look at the white spacer first! Another shop installed a BRAND NEW carb, with no difference to the performance, so I'm hoping it has something to do with the jetting. If not... maybe as suggested above- the electrical system.

Title: Re: Carburetor doesn't seem to like heat!
Post by justin_o_guy2 on 05/27/10 at 08:42:54

Did you get the old carb? Have you looked at those jets?

If youve had the carb replaced w/ no change in symptoms, wouldnt that make looking elsewhere seem more reasonable? Or is it just so much easier to mess w/ something that can be held in a hand than that scary ol' 'lectrical stuff? Heck, Id probably start on the carb, just hoping to dodge an electrical issue..That stuff can be such a hassle.