Suzuki SV650 Riders Forum banner
1 - 20 of 25 Posts
G

·
Discussion Starter · #1 ·
Hi all,
I'm new to this so bear with me. I just picked up a 2001 sv650 and I think it's running lean. I get this surging between 3500 - 6000rpm. Everything is still stock and I'm pretty sure the previous owner didn't play with the carbs. I read about shimming the needle but I don't know whether or not I should use one, two shims....? Any help or suggestions would be appreciated.
 

·
Registered
Joined
·
6,503 Posts
Pull the plugs and look at them. If they are too light then you are too lean. If they look OK there could be another problem. Lean is the most likely reason.

Also, adjust the idle screws to give a good idle after you've added a shim (if you're lean). The idle screws should be as far in as possible while still giving a steady throttle and good response off idle. If you have too rich an idle the transition can be sluggish. It's an iterative procedure. Using the idle screws to make up for the needles' leanness is not the best practice. It might work, but it goes against best practice.

Not all SVs are lean. Mine ran very rich. My idle screws are barely more than one turn open, I punched 4 holes 5/16" diameter in the muffler baffle to get it right. It's sharp and crisp and the plugs run a perfect light tan color.
 

·
Registered
Joined
·
413 Posts
To make sure it's a lean surge get the bike warm, then on an OPEN and preferrably UNINHABITED straightaway get the bike up to the rev range where the surging occurs. Gradually apply choke and see if it goes away. If it does shim and fix idle screws, if not look elswhere.
 
G

·
Discussion Starter · #7 ·
I haven't had a chance to work on it yet, but if it isn't lean surge what are some other possibilities?
 
G

·
Discussion Starter · #8 ·
Lean surge fixed! I have a 2002 sv650s with 1700 miles that was stored for 2 years. It had the dreaded surge just off of idle when cruising at anything below 40 mph. After much reading on this forum and cleaning carbs, adjusting pilot screws, etc, I found that the needle shim fix worked perfectly. I moved the shim (washer) already on top of each needle C-clip to just underneath it according to catpoopman's video (in Tips n tricks). By the way, I also have a TB carbon slip-on that may have something to do with why it happened in the first place.
 
G

·
Discussion Starter · #9 ·
I've had a chance to shim the needle. I started with one Shim and so far its made little difference. I am going to try a second shim tomorrow. Any other suggestions. Could it be that the carbs are out of sync?
 

·
Registered
Joined
·
536 Posts
Yeah, carbs out of sync can cause that, too. Fortunately, a home-made carb sync tool is really easy to make with some zip ties, a piece of 2"X2", some aquarium tubing and some heavier-weight oil.

Also, I noticed that you have a used bike. I'd recommend checking the chain for tight spots, which can in theory cause surging/loping, too. You never know how well the PO actually took care of the chain.
 

·
Registered
Joined
·
1,103 Posts
KBC said:
I haven't had a chance to work on it yet, but if it isn't lean surge what are some other possibilities?
plugged needle jets can cause a surge too. in that rpm range. had the bike been sitting for a while?
 

·
Registered
Joined
·
166 Posts
I have the same problem, only it's really noticable in 1st gear at 2000-3000 rpms, like when I'm in stop and go traffic( which is usually stopped more than go on the way into work). The PO of my bike probably had it sitting up for a long while, since it's a 2000 SV and it only had 1900 miles on it when I got it a few months back.
Is there somewhere online where this "shim" procedure is explained?
thanks
owl
 
G

·
Discussion Starter · #13 ·
I added the 2nd shim and still have the surging feeling from 3,500 to 5,500 rpm. I replaced the plugs while I was in there and the old plugs looked like the bike was running lean (white/chalky look). It might be a combination of factors. I'm going to borrow a friend's carb sync tomorrow and see if that helps.

As for the chain I probably need to replace it. I don't know its history. I did check it out and it doesn't seem to have any tight spots but it has been stretched.

Owl: Check out the tips and tricks section. There is a great explanation there by John Callahan.

Shimming the needle did increase the punch factor in the 3-5k range, which is nice.
 
G

·
Discussion Starter · #15 ·
I have'nt touched the srew yet. I've been a bit nervous to start messing with Air Fuel Mixture. I imagine having to pull the carbs off twenty times in order to fix what I screw up.
 

·
Registered
Joined
·
109 Posts
Not to worry.

You might have to do a dozen times to get if PERFECT, but once or twice will get it really close.
Find out at least where it's at, and if it's not a fairly normal value (2.5 turns?) you can always tweak it.
 

·
Registered
Joined
·
118 Posts
Hi, I was really happy to see someone posting about this, before I did.
Was just going to ask about lean surge.
Mine seems to occur right at 4k rpm. Like if I'm trailing behind a car I want to pass soon, and am just hanging there...has what I think is lean surge. My old bike had it too (Magna) and I never did anything about it. Same exact symptom.
I know on some bikes, like for instance my project bike, Yamaha XS650, sometimes the lean-ness can be taken care of with *just* turning the air mixture screws out say 1/2 a turn.
I'd like to try *just* this before actually taking the carbs apart enough to shim the needles or set them up a notch (not sure which way these work).
Was wondering if anyone had done this. i.e. *just* turning the airscrews each out by exactly the same amount, just a bit.
ALso, on the SV, do you have to drill out "plugs" which cover/hide the airscrews?
I know it was that way on the Magna, and originally on the XS too, altho those have long since been drilled out.
So, basically I'd like to hear from someone who was able to fatten things up a bit just by turning out the airscrews. Or if someone tried that and it didn't work.
I guess I'm thinking it might NOT work because the lean ness I'm experienceing is at a higher rpm, that might be better addressed with the needle shim.
thx
Em
'02 SV black bike, stock and untouched, 3200 miles on
 
G

·
Discussion Starter · #18 ·
Em-- I tried 3 turns and 3.5 turns out on the pilot screw with no change to the lean surge whatsoever. One shim under the needle worked.
However, now I've still got them at 3 turns out, but warming up with the choke is very rough. As soon as I can get the choke off without stalling, it runs great. It was smooth as butter when I had the surge and no shims. I'm going to put it back at 2.5 and see if I can get no surge AND a good warm up at the same time. '02 sv650s, 2000 miles
 

·
Registered
Joined
·
109 Posts
Yes, you will need to drill out plugs.

Though I've had success with quite a few carbs by backing mixture out 1/2 turn just as you have, it doesn't seem to effect the midrange much on this particular carb/cam/motor combo. Worth tyring.

FWIW, shimming the needle is actually a lot easier than turning the mixture screw, given you have to drill out the plugs. I still think you should drill and turn, but since you were commenting on doing the easy thing (mixture first) I just thought that I'd mention you'd picked the wrong one as easiest.

hth
roger
 

·
Registered
Joined
·
118 Posts
ferretface said:
Em-- I tried 3 turns and 3.5 turns out on the pilot screw with no change to the lean surge whatsoever. One shim under the needle worked.

Hi Ferretface (is that what you go by here)?
:) ok thanks for the info, much appreciated.
Em
 
1 - 20 of 25 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top