My Project: Make this 1993 Reliable

[casezero]

Hope this counts as a project. Bought a bike a while ago that was in pretty rough shape. Didn't really realise how heavily modified it was until later on. It was running OK before I last took it apart, but definitely not great. Had frequent issues with fuel leaks, and an awful gas tank. I've never owned a carbureted bike before (I've had two 2003+ SV650S, and I loved them to death, so I wanted another Suzuki) so I figured I could get it running better. It's worth mentioning that I have no legitimate mechanic experience, but I managed to keep the SVs running by figuring it out as I go.

This is more or less the shape I purchased it in

Original info:
-Main Jets: 152.5 (L), 145 (R)
-Idle Jets: 40
-Pilot Screws: 2.25 turns (L), 1.75 turns (R)
-Needle jets: 2 washers (?)
-K&N Lunchbox Air Filter (w/ vent filter on the breather hose)
-Muffler MIA
-Left float needle was missing its little clip part

So far I have...
-Checked spark plugs (They were black - esp. left side - so I understand it was running rich previously. Will be replacing them soon.)
-Pulled carbs, air filter, gas tank
-Replaced main jets w/ 147.5
-Replaced idle jets w/ 40
-Set pilot screws to ?? (currently at 1.75 turns out)
-Replaced fuel tank, tank petcock, & filter
-Replaced Fuel lines w/ Tygon tubing
-Used spare Tygon for overflow tube from tank (how was this missing?!)
-Cleaned carbs & replaced carb gaskets
-Set float heights (Tried to be meticulous, but all I had on hand was a ruler. Used some tubing to check them later and they look OK.)
-Changed oil & oil filter
-Topped off with fresh gas & air in the tires

So at this point, the bike starts, idles, and is somewhat ride-able, but definitely not where I'd like it to be. I spent a good portion of today just trying to get it warmed up, adjust the pilot screws, and adjust the idle speed thumb-screw, but something is still funny, so I'm trying to come up with more ideas before just tearing everything apart again.


Basically the bike seems like it wants to die at idle no matter how many turns in or out I give the pilot screws... Well, if I open them up more than 2 turns it seems like the bike gets really sluggish and struggles, so I settled on leaving them less than 2 turns out. Then when trying to adjust the idle-speed screw it seems like either the idle falls too low and stumbles, or if I go in then the RPMs get hung up and rise to ~5k. Also when I got in from my test ride, it seems like the choke isn't doing anything anymore. Action looks right, and it seemed to make a difference before I left. While riding, it seemed like the bike would sputter from idle, but then the RPMs would catch and climb, and it felt like they weren't falling like they should when I let go of the throttle. Also worth noting: all symptoms appear to persist regardless of whether petcock is set to On, Res, or Prime.


Current thoughts:

I know I'm going to hear that it's stupid to run it without a muffler, but I don't have one currently so I don't have much choice right now.
I would really like to get a short, nice-sounding exhaust to put on it one day, but I'm pretty limited in my machining resources and mufflers are expensive.

I'm thinking that the main jets are probably too large, but it's just a hunch and I still don't feel like I totally know what I'm doing. I have spares (125, 145, & 150). Could the main jets alone be the primary source of my woes?

It seems (in my limited experience) like the bike is still running rich at idle, but then there's an air leak or something that carries the RPMs away, and they tend to get hung up. I tried checking for a leak by spraying some WD-40 around the intake manifolds, but got nothing. Not really sure what I'm going to do about it yet.


Current look


Still to do:

-Change chain/sprockets
-Replace spark plugs
-Figure out something regarding the muffler situation
-Probably other stuff I'm forgetting at the moment


Instead of posting individual photos here, I just uploaded everything I have so far as an imgur album. Be warned, I took a lot of pictures...
Picture album

Also, here's a video of the idle after I got back from my test ride earlier. I'm on an ever-so-slight incline, so maybe that's why it's behaving a little less wildly, but usually with a rev it either behaves as it did in the video or the RPMs get stuck up around 5k.
Video of idle

If anyone has any thoughts/suggestions, I'd love to hear them. Cheers!

Edit: added a couple photos to break up the wall of text.

[ShowBizWolf]

Hi casezero,

I liked reading your story/details about your GS! I really wanna check out the pics but imgur doesn't load right on the work computers      I'll check it out when I go home!

I hope you get your bike sorted... I wish I could help but I'm sure others will reply soon and get you heading on the right track! You brought up a good point about no muffler... I feel like your issues with getting the bike running properly would be so so so much easier with a stock muffler and then once you got everything right that way, you could get into modifying things from there.

Hopefully Buddha will see this and offer help with the jets and whatnot 

I'm looking forward to seeing more of what you do. Good luck!!!

[lucas]

Recently I installed a baffle in my exhaust and it completely changed the horsepower output which led me to believe that even small changes to the exhaust back pressure can have big consequences when it comes to performance.

I got my muffler from Ryca.com rycamotors.com. Was inexpensive, good quality, and sounds good (to me).

If your choke lever is not doing anything then maybe you have an air leak in the top caps that are preventing the slides from lifting (effectively making it so it is always choked).

Run the engine with the air box off and watch the black plastic slides, if they don't both rise up and hover while idling then the proper vacuum isn't developing above the rubber diaphragms.  In that case you should inspect the diaphragms, the cap, and the little nipple covers on the caps.

[gregjet]

Let me just check you facts cause I am getting a bit confused from the post.
Are the following correct.
Turning the idle screw doesn't make any difference.
Applying the choke seems to make no difference.
If this is the case one or both of the choke circuits may not be closing off. Could be external ( in the cables, linkages) or internal ( seals, blocked air channels etc.)
What ever you do it won't run properly with no muffler on the same jetting as with one. Even at idle.
Also check the filter isn't overoiled.

[casezero]

@ShowBizWolf
Well thank you for checking it out! Definitely having some sort of muffler to work with would be preferable, especially since I'll almost certainly just have to rejet and tinker all over again when I do finally get one. It's really just bugging me that I know idled and accelerated noticeably smoother before my tinkering, despite all the things I felt like I "fixed" (hah) so while I'm sure it won't be perfect yet, I'd like to at least get it consistent for now.


@lucas
That's interesting. I always see back pressure brought up, and it makes the whole exhaust system really intriguing to me. The term "back pressure" itself seems kinda baffling to me, but it does make sense that bends and constrictions have a huge effect on the flow of exhaust gas. If only I had nice equipment to play with, I'd love to to just test the effects of little changes throughout RPM ranges and what-not.

Was it perhaps rycamotors.com? Looks like they've got lots of stuff, so I'll try to check it out soon. Have any suggestions on what to do with it? Should I just look for a bolt-on piece that will fit the headers I have?

As for the suggestions regarding the carbs: that's brilliant & exactly the kind of thing I was hoping others would point out that I would overlook. I'll definitely give it an inspection next chance I get. Much appreciated!


@gregjet
Fair enough! Sorry, I tried not to ramble too much. Here I've been calling 1 the pilot screws and 2 the idle speed screw.

I'm not sure if my terminology is consistent.

Last I checked it: Turning the 1 screws less than one turn out seemed that the bike would die. Turning them more than two turns out also seemed to result in sputtering and stalling, despite playing with the thumb-screw (marked 2).

After being sure it sufficiently warmed up, I left the pilot screws at 1.75 turns out. Turning the thumb screw out would reduce the runaway RPMs, but lead to stumbling idle and occasional stalling. Turning it in a couple turns would help bring the idle up where it needed to be, but then it intensified the run-away RPMs.

No, the choke does not seem to make a difference now.

Any opinions on what I should be looking for with regard to isolating the choke issue? Like how would I know it's the linkages vs seals? And the filter looks kinda dark. I haven't applied anything to it. Might try to clean it up and give it a spot of fresh oil or something. Never had a K&N filter before.

Last: I realise that about the jetting with/without muffler, but like I say, I just know it could be better in the meantime, and I think the only thing I really changed was the main jets... unless I buggered something up in my tinkering. It's always been a little droopy about starting off in first gear, and then picked up at 3k+ RPM, but it just seems seriously exaggerated since all my rebuilding.

Thanks for the replies!

[ShowBizWolf]

oooo you added a couple pictures I can see!! I like those clubman bars... are you gonna keep them/do you like them? I hope you do cuz they look cool 

[casezero]

I sure did!  And yeah, I like the bars as they are really, so I'm planning to leave them. Glad you like them! 

[NighthawkNFLD]

I also wish I could give you some detailed help but I never really had any troubleshooting to deal with during my project. I basically just replaced my main jets with 147.5's (now 150's) when I opened up the intake and the exhaust. It doesn't like to idle until it's FULLY warmed up but besides that I have no problems with run ability or performance at any speeds.  Maybe I just got lucky haha.