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Message started by redsavage87 on 06/23/10 at 18:13:24

Title: Intermittent surging/bucking problem
Post by redsavage87 on 06/23/10 at 18:13:24

My bike has recently starting doing this thing where it will surge, sputter, and backfire, almost like it doesn't have a steady fuel flow. Sometimes it's not that bad, other times it's so bad it's practically bucking me off the bike when I'm accelerating. It doesn't appear to have any dependance on the weather, or if the bike is hot or cold. It's completely random too. I've had it so bad I almost drove it straight the the mechanic, then had it stop and not do it again for a week.

I did have the mechanic check it out and I don't think it had any problems for the 3 test runs he took it for. He thought it might have something to do with the exhaust I have on it, (the previous owner put it on, I don't know anything about it) and it not creating enough back pressure for the carb. He told me he thought the engine was running strong and the bike was carbureting well.

Any suggestions?

Title: Re: Intermittent surging/bucking problem
Post by bill67 on 06/23/10 at 18:22:03

I would run some Sea Foam in the gas see if that helps.

Title: Re: Intermittent surging/bucking problem
Post by prechermike on 06/23/10 at 18:26:11

Do you by any chance, have a 87 savage? When my 87 started bucking it was the white spacer. take the top of the carb off, replace the spacer with a nylon washer and put it back together. Search for white spacer and you should find it. It was not hard to do.

Title: Re: Intermittent surging/bucking problem
Post by Serowbot on 06/23/10 at 18:31:00

Test your Petcock...
see here...
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1251932429

Title: Re: Intermittent surging/bucking problem
Post by verslagen1 on 06/23/10 at 20:46:35

yep, see if it does it in prime.

then check the kickstand, if it doesn't hold up over bumps then it'll cut out.

Title: Re: Intermittent surging/bucking problem
Post by Routy on 06/24/10 at 06:01:43

When you have an at random intermittent problem such as you describe, you can almost always rule out any solid state component,.....such as the white spacer, and/or a modified exhaust system. Of course this would exclude a poor wiring connection etc etc.

You said it does it mostly under acceleration ? If so, you can almost always suspect a malfunction in the main fuel delivery, such as the vacuum supply to the petcock, or a partially blocked fuel filter or fuel line,.....and in that order ;)

Title: Re: Intermittent surging/bucking problem
Post by Bubba on 06/24/10 at 06:57:34

I vote petcock...try running it on prime for a while and see if it goes away....make sure you keep filling up the tank tho'

Title: Re: Intermittent surging/bucking problem
Post by redsavage87 on 06/24/10 at 14:03:08

Thanks for all the suggestions guys! I checked out the kickstand, it's holding up just fine. I've been running it in prime and haven't had any problems yet, but I'll have to drive it around for a bit to be sure.

Also, it does seem to do it more often when I accelerate hard (i've been trying to see if I can do something to make it buck) but it does do it at a constant cruising speed as well.

Thanks again! I'll let you know if I find anything out ;D

Title: Re: Intermittent surging/bucking problem
Post by thumperclone on 06/24/10 at 14:10:07

big heel on your boot hitting the kickstand???

Title: Re: Intermittent surging/bucking problem
Post by redsavage87 on 06/25/10 at 17:17:17

It's an 87. The kickstand doesn't appear to have any effect at all (I can ride around with it fully extended down) and it's doing it when the bike's set to prime too. I'll check my fuel lines and test my petcock, see if I find anything...

Title: Re: Intermittent surging/bucking problem
Post by redsavage87 on 07/07/10 at 21:48:52

Hey guys, thanks for all the help! I think I may have found the problem. I replaced my vacuum tube (it was kinda old, but didn't have any cracks or anything...). Since I've done that I haven't had any problems. It's been over a week, but I'm keeping my fingers crossed.

As for that white spacer in the carb: I have been having some issues which I think are carb related. Mostly backfiring when I let off the throttle (which I know is pretty common) and I'm even getting some flames out the back of the exhaust. It's not a stock exhaust, the guy who had the bike before me put it on, and apparently didn't tune the carb to match it. I took out the white spacer, which didn't seem to do a whole lot... maybe make it backfire louder... I think I'll end up replacing some of my jets with different sizes. :P Don't you just love tuning a carb?

Title: Re: Intermittent surging/bucking problem
Post by verslagen1 on 07/07/10 at 22:16:20

[smiley=thumbsup.gif] vac line

back fire on throttle close can be loose header bolts or muffler clamp.
How's the pow on shutoff?
could be you just need to richen the idle mixture a bit.

Title: Re: Intermittent surging/bucking problem
Post by redsavage87 on 07/21/10 at 23:46:49

Still no problems since I replaced that vac line! Looks like that did it. Thanks for all the help guys.

As for the backfiring, I turned out the pilot air jet a turn and took out the white spacer. Still backfires, but it's much, much better. Gonna get a hold of some washers and try it at 1/2 spacer, see what that does.

Title: Re: Intermittent surging/bucking problem
Post by DrunkenDwarf on 07/22/10 at 06:03:47

1205041301160107055857600 wrote:

As for the backfiring, I turned out the pilot air jet a turn and took out the white spacer. Still backfires, but it's much, much better. Gonna get a hold of some washers and try it at 1/2 spacer, see what that does.

+1 for 1/2 spacer.

-Gak Toid

Title: Re: Intermittent surging/bucking problem
Post by Routy on 07/23/10 at 05:23:07

Quote:
Don't you just love tuning a carb?
------------------------------------------------
Yes, but only when I know where I'm at, and why I'm doing it.
Modding a carb for an inconsistant problem, is normally not the answer.
Some here are modding carbs as just a shot in the dark ::)

Title: Re: Intermittent surging/bucking problem
Post by Charon on 07/23/10 at 06:06:42

There is an old saying - "Carburetor" is French for "Don't muck with it." Like shooting skeet, there are a lot more ways to miss the target than hit it.

Title: Re: Intermittent surging/bucking problem
Post by Bubba on 07/23/10 at 07:36:36

Here's what I did to my carb. I'd never messed with one before but after joining the forum I felt like there were symptoms I had that could be corrected by working on the stock setup. Mind you, I had put an after market exhaust on but as I worked through the issues I found that taking things slow and doing one thing at a time to see the results worked out well for me.

1st mod was to change the needle jet spacer to a #4 nylon spacer from ACE. Eliminated the surging in the mid range I was getting from day one.
Changed to a 150 main jet after a month or so to improve the high end some...that worked!
Still had the POP on shutdown and pops between shifts (pretty sure I don't have air leaks in the exhaust)
Threw in a 52.5 pilot jet with bleed holes and that (almost) eliminated the shutdown POP but still occasionally get pops between shifts.
Fine tuned the airmix screw to 2 1/4 turns out.