SuzukiSavage.com - Print Page

SuzukiSavage.com
/cgi-bin/YaBB.pl
General Category >> Rubber Side Down! >> Rough running in midrange
/cgi-bin/YaBB.pl?num=1180738074

Message started by borne2fly on 06/01/07 at 15:47:54

Title: Rough running in midrange
Post by borne2fly on 06/01/07 at 15:47:54

Got the cylinder head back on and now it is hard to start and runs rough even after it warms up, particularly in the midrange (guessing 2000-3000rpm). Never fiddled with the carb other than to disconnect it from the head. Pulling the choke out a little seems to make it run smooth. The spark plug is new. Total mileage is around 15K. I've looked all over for air leaks and can't find one. Any ideas?

Title: Re: Rough running in midrange
Post by BornOnFire on 06/01/07 at 17:19:00

It's possible that you may have debris on the inlet side of the carb somewhere due to the top end rebuild? You may have to finally tear into it. Sounds like a definite fuel issue if the choke improves it.

Title: Re: Rough running in midrange
Post by borne2fly on 06/01/07 at 18:02:12

If that's all it is I'll be a happy guy. I was planning on rejetting it anyway to ease the backfiring problem, but I'd like to get it running the way it use to before I mess with that.

My fear is that I'm off one tooth on the cam timing. When I put the timing chain back on I lined up the crank to TDC using the inspection window on the left side, and tried to line up the cam as per the manual. But (as usual) the perfect cam alignment put it "between teeth" on the cam gear, so I was forced to guess which tooth to engage, slightly advanced or slightly retarded. In retrospect, with 15K miles on the bike I should have realized that this was probably due to chain stretch and that would have led me to engage the cam gear on the slightly lagging position. If I got this wrong, would that account for this sort of rough running? Somehow I think not ..... I imagine that if the cam were misaligned no choke setting would help (fingers crossed).

By the way ..... welcome to the board Newbie! The bike I'm working on belongs to a girlfriend and she loves it. I've always had a fascination with big singles, they stand in defiance of overcomplicated, over-engineered machines. A blast from the past :)

Title: Re: Rough running in midrange
Post by borne2fly on 06/01/07 at 18:04:26

I'll run a compression check on it in the morning. Anyone know what's a normal reading?

Title: Re: Rough running in midrange
Post by barry68v10 on 06/02/07 at 03:32:40

I don't have a service manual handy, but I'm thinking:

14.1 atmospheric times 8.5:1 compression equals real close to 120 psi. Although I would think anything over 100 psi and you're good to go. Can anyone confirm or deny this?

Title: Re: Rough running in midrange
Post by borne2fly on 06/02/07 at 10:32:39

It's fixed now. Turned out to be nothing more than an idle screw adjustment. Now it's around 1.5 turns out and everything runs well. It's amazing how much influence this setting has over not just idle but the whole lower half of the power range.

Title: Re: Rough running in midrange
Post by justin_o_guy on 06/02/07 at 16:08:29

I went out & cranked the throttle & watched the idle adj. I cant see that it does anything more than if the throttle cable was adjust exactly to achieve the idle speed desired.Looks to me like the idle adj. does nothing more than set the lowest fuel delivery the engine will see. Also, it looks to me like if I set the idle low enough that I had to hold the throttle slightly open to keep it running, it would have zero adverse effect on the engine running at speed. anyone able to help me understand how I am incorrect here?

Title: Re: Rough running in midrange
Post by borne2fly on 06/03/07 at 02:01:18

My mistake, I meant to say "idle air screw".

Title: Re: Rough running in midrange
Post by justin_o_guy on 06/03/07 at 04:54:45

Ahh, okay, thanks, I was scratching my head for a while,, Yea, I can see how that one would mess things up a bit.