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Helping my GS1000S breathe................

  • Thread starter Thread starter terry
  • Start date Start date
T

terry

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Ive owned a 1980 GS1000ST for the last 3 or 4 years, it was stock when I bought it, but I've since added Yoshimura 1100 pistons (approx 11.5 to 1 comp) Yoshimura stage 2 cams and heavy duty valve springs and a Megacycle pipe in the last 12 months or so. Initially I had problems with plugs fouling, but I've since fixed that by replacing the old coils with new suzuki items. (it's got the factory electronic ignition, and my dealer tells me that these rarely gave any trouble) I probably should have bought dyna or accel coils, but the suzy items were cheap and seem to work ok. The trouble is it still seems to be running rich. I've dropped the needles one notch from the centre position (33mm factory Mikuni slide carbs) and am picking up a "high flow" foam air filter this week as well, and looking at my old Yoshimura catalogue, they mention that the air filter box should have some extra holes punched in it to allow better air flow. My question is, has anybody out there in GS land tried this, and where's the best place to punch the holes. I've looked at my airbox and there are already 2 "quarter" sized holes already punched in it from the factory, are these sufficient, or do I need some more? Would leaving the lid off (the new filter is an "oiled foam" type) have the same effect? Apart from running rich across the rev range, it goes like stink, and will rev to 12000 RPM in 3rd gear (that was at 120 MPH and I decided that I didn't need to explore it's outer limits) with the standard 15/45 gearing. I run it on Shell Optimax 98 RON unleaded, which is the best I can buy here in Australia without going one step further and buying aviation fuel. The carbs came off another GS1000ST I own (I have three, plus a GS750) which is stock except for a megacycle pipe, and the donor bike didn't run rich when I rode it before the carb swap. :twisted:
 
In the early & mid "80"'s Vance & Hines recommended removing the lid from the air box. This always worked pretty good for me.
 
If you are not afraid to play, youcan go as far as you want to
P2190003.jpg
 
P2190004.jpg

The yellow lugs are the extra ground wires and there are more of them wherever i could sensibly place them. all soldered also.
 
P2190005.jpg


The K&N is modified by using a piece of vent pipe and some permatex black to hold it together.
 
I used some yellow tape and O rings to make the temporary setup fit properly. It is not as good as the next modification will be.
P2190006.jpg


I have another air box and larger carbs that will go on next. I will make the hole in the new air box larger and also will cut some of the foam out of the K&N to allow for more air to flow. I have 150 mains now and i believe i may have to go to 160s but testing is the only way to know for sure. Make sure your exhaust is a good one though. Not just the brand but what is is designed to do
 
Scotty.................what carbs are you going to install? and why not use individual k&n filters?.....skip
 
skip[ said:
Scotty.................what carbs are you going to install? and why not use individual k&n filters?.....skip
Click to expand...
I believe in understatement. I will be installinf 36mm semi flat slides from a 1996 750 KAT. I already have them and have convertesd them to a pull choke mounted directly on the carb rack.
I want the still air effect so i can still ride fairly normall yet with the air box mods i expect to get the same results as one gets by running pods and still retain normal drivability. When it done i will still have to tune the setup but only testing will tell if my idea will work.
If not i wil have to get crazy DAVE O in on the project. He helped me to reverse my shift pattern. A real wack job he is but an excellent mechanic and improvisor.
 
Helping my GS1000S breathe...........

Helping my GS1000S breathe...........

Thanks guys, I'll try just leaving the air box lid off and do a "plug chop" first, then if it's still running rich I'll pull the carbs and drop the jet sizes somewhat. I did a compression check a little while ago, and it was making between 170-180 psi. I know that this is well within spec for a stock engine, but I couldn't find the specs in my Yoshimura book for the 1100 kit? Does anyone know what I should expect considering the 11.5 to 1 pistons are a bit of a jump up from the stockers? Hey Slopoke, nice bike mate, thanks for the pics!:twisted:
 
Terry, there are two conditions you may want to consider...first, that the OEM coils aren't hot enough to light the mixture on this combination at low rpms, thus blackening the plugs. Second, with the different carbs/cams/pistons/etc. a combination can be realized that causes the intake gases at a certain (i.e. low) rpm to pass through the carbs, reverse direction after bouncing off the head of the intake valve going backward through the carb a second time, then again passing through the carb after the valve opens. This clears out after the rpms increase, but at low revs it causes fuel to be picked up three times before burning. I know this can be explained better but indeed occurs in some modified engines. Higher revs and plug chops won't shw it. Good luck.
 
Slopoke wrote:
He helped me to reverse my shift pattern.
Click to expand...

Dom, I'm just curious. Why would you want to reverse your shift pattern?

Blaine
 
Junkman Frankenbiker said:
Dom, I'm just curious. Why would you want to reverse your shift pattern?

Blaine
Click to expand...
I cant answer for slopoke but I can tell you that when I used to drag race my bike I would switch my pattern also. I did it for two reasons first , I found I could shift faster stepping on the shifter than pulling up on it, and second I use an electric shifter that kills your coils for a micro second so you can shift with out using your clutch. The normal g- force you get under acceleration wold make you lift your foot and somtime kill my coils prematurely causing the bike to die till you got it in the next gear. Reversing the pattern eliminated it.....................skip
 
Rich running

Rich running

Try Accell coils(bolt straight on) and one large K&N (100mm by 160mm I think mine is) air filter clamped onto the back of the first part of the airbox
 
One point to bear in mind is that shell optimax is a high density fuel. The bike may run differently on optimax compared to normal premium unleaded. It may be an issue if you jet for optimax then have to use something else. The effect seems to vary bike to bike, some not even noticing a difference

I use premioun unleaded rather than lead replacement fuel, even tho LRP is supposedly higher octane. The bike runs smoother and carburates much better with PULP (I have a 1080 kit, stage 3 cams and ported head on a GS1000 1978 - 2 valvers are not as efficient combustion wise as 4 valvers) LRP supposedly leads to more carbon build up as well..so avoid!

Oh yes, I am in canberra
 
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