33mm smoothbores work on 79gs1000?

[79gs1000l]

Man i hear that saaz! I can't wait for this thing to start working so I can stop working. OK, so the air screws were at most 1/8 of a turn out. I put them at 1.5 turns at that made a huge difference. How do the airscrews work? because now it idles smooth, very smooth, better than my stock carbs did, and it is very smooth at constant speeds. (before it would stutor if i wasn't accelerating) and it is no longer rich it is actually lean. The screws made a major difference in the low end operation, but now it doesn't run right upstairs. (typical, solve one problem create another). It runs so nice up to about 3/4 throttle. I had in some 137.5 mains but they were lean and the transition form mid to high range was very rough. so i put in some 143.8 mains and now i can't run high end cause it just stutors at the top end of the midrange. My air screws are out 2 full turns ( i wanted to see if it would act different from 1.5 turns, which I can't feel any difference but I realize that does not mean i didn't screw things up) And I moved my needle clip back from the middle position to the lower position raing the needle up. I did this because the plugs came out white with the clip in the middle and I hoped it would help the stutoring problem which it did slightly. The plugs still come out white, probably cause I can't get on the main. I do not yet know what pilot size i have in, but that wouldn't affect the high end would it? SO should i turn the screws in to 1.5 or 1 turn out should i lower the main or raise it. should I move the clips on the needles. which one should I do first? sorry for the long post but thank you guys so much for the help.

 

[saaz]

The pilot circuit should be set within 1 1/2 turns. If you have to go nearly all in or out the pilot jet needs changing

There is a diaram on the net explaing the ranges within which the different circuits operate (the US mikuni site?) which may remove some of the mystery.

Usually you need to get the main right before you can dial in the needles. Pilots are low down, interact with the slide coutout a bit further open, the needle does most of the work in the mid/upper end, wide out the main.

The pilot does not affect wide open. If it runs ok to 3/4, the needle is probably about right, the main is at fault. You may find that as you get closer on the bigger main it could cause the midrage to run a bit richer, so you may have to lower the needle. Some fiddling may be needed once the main is right to get the mid range right.

There is also the option of chnaging needles as the profile will make a difference, but this is getting a bit serious!
Good luck. I will be out of action for 2 weeks, so hope you are all done by the time I am back again!

 

[79gs1000l]

If I haven't got it figured out within two weeks then it is obvious to me that these carbs weren't meant for this engine. That would leave the only option of finding an 1150 engine to replace the faulty unit. :wink: but until that time here is what is happening. bike runs great up to 3/4 throttle. when i get to 3/4 it stutors like crazy; if, at this time, I go to full throttle it cleans up until is gains about 1000 rpm's and then it stutors again. I will try to get the main right, but right now i can't use the main as it stutors horribly. so i guess i will have to mess around a bit to get things working.

Just a side ? is the 1150 engine dramatically faster than the 1000. I have read just about everything i can find on them. and they seem pretty awsome. what kind of power could one expect from a mildly built one. suppose it had, well 33mm smoothbores, a ported and polished head, megacycle street cams, and a nice exhaust. everything else stock? would it be pretty streetable?

 

[saaz]

The 1150 motor is a powehouse standard, let alone with a little work. It is easily in the same territory as the 1200 bandit, and is used as the basis of drag bikes now.

There are a few 1150 owners on here, so perhaps put in a general quesation.

On the carbs, with such big carbs on a relatively standard motor there may be some time needed to dial them in. My motor is hotted up but can really only take 29mm smoothbores due to the intake manifolds...matching the 33mm with the ports is a real issue.

If it is now stuttering nut was only lean before you may be getting to the sensitive area of too rich...try a reading of the plugs. Big carbs are a bit painful to dial in as the engine is not sucking consistently enough to get clean readings

 

[Anonymous]

33mm smoothbores are not to big for a 79 1000. If your still have the stock exhaust on the bike it will make tuning them very hard try stuffing a patatoe in your car exhaust see how long it runs the exhaust should be changed first. or if the bike has low compresion it will need a larger main and richer emultion tube. I have a costomers GS 1000 Iam doing chassie work on in my garage that runs great with 33mm smoothbores on it I will pull the jets and post the sizes for you sorry about my spelling

 

[Gerry]

Just to let you know a little about the 1150 motor. Mine has a 1199 kit, ported for 38mm smooth bores, dyna ignition and coils and a pipe that has no restriction in it :lol: I had it on a dyno three years ago before I put a new clutch in it. The dyno read 72 lbs of torque @3500 rpm and 81 lbs @ 6300 at the rear wheel. The horsepower was 99 @ 6300 this is when the clutch slipped a little, it went as high as 104 @ 7200 rpm but I don't know how true it is after the clutch slipped a little. If you add the cams, 8O :lol: :lol: My bike is very street friendly, hope this tells you what you want to know about the 1150 motor.

 

[79gs1000l]

Thanks stretracer. the jet sizes would be appreciated. I still have on the stock exhaust. this spring i will get a vance and hines set up. right now I have in 135 mains. and the clip on the needle is one lower than the middle. I think the main is a little large. I went to a mikuni site and they recommend the "roll off" test for main size. Basically you get into fourth gear and open her all the way up. after she is pulling good and hard back of the throttle just a tiny bit. this will lower the slide a small amount richining the mixture. If it increases in power then the main is to small. if it stutors the main is to large. Mine had more power with less throttle when I had in 115 mains. and the 135 mains stutor. so I will next try 130 mains. And what is a emultion tube?
Gerry thanks for the input on the 1150. 72 pounds at 3500 and a 100 horse by 6300 rpm must make for a fun ride, talk about a large power band. I read in cycle world about a new kawasaki zrx 1200 that had been hopped up that also had 100 horse at 6000. only they had to use 1300 cc's and some new cams to do that. Of course it ended up with 150 horse up top. Makes me curious about what yours would have been if the clutch hadn't slipped. What do you guys think about the possibility of replacing my 1000 with an 1150motor. :twisted: do you think it is possible to get 150 horse out of an 1150 with the modifications I mentioned. If so my 1000 motor is out the door :!: :!: would the 33mm carbs be big enough? could I get a pipe to fit that motor and my frame?

 

[Dink]

the 1150's had 125hp stock (measured at the crank I believe)so 150 rear wheel may be a bit unstreetable but 140 would be easy.
the motor should bolt straight into your frame, with the possible exception of the rear upper engine mount which you would probably need to fabricate.
the exhaust should fit with slight mods which any exhaust place could do,i.e. a slight re-bend at the bottom of the motor.
Dink

 

[skip]

My 1150 motor has not been on the dyno yet but I have had lots of trips down the 1/4 mile. 140 hp is probably about where i am. I say this because my friend dynoed his 2 valve 1327 cc kaw dragbike @147hp and with very simmilar gearing he only ran 4 mph faster than my bike. his bike and rider combo is 75 lbs lighter than mine and with the slick and wheelie bar he can run wide open from the start.( I cant) We both cross the finishline at 9500rpm he runs close or just over 140 mph and mine runs about 136. my motor is 1229cc and I run cam motion g-4 cams a mildly ported head with oversized valves and 38 mikuni flatslides. I have all dyna electronics, coils, ign,rev limiter. My motor was run hard for many years (14) and with nitrous many times. I only had to rebuild it once. These motors are almost indestructable.

 

[skip]

Just a remider. when you started this project a few of us told you to get the header first. I realize that this was not in your plans or maybe budget. Now you can see why we suggested this.You have so much time invested in tuning you carbs and you sound like you may be getting frustrated. When you do get you exhaust from vance and hines you will have to do this all over again but you will definitly see the improvement in performance. Also by then you will be an expert in carb tuning! dont give up, hang in there and good luck.....................skip

 

[lhanscom]

Also, once the headers are put on, and increase the air flow, it should make tuning the carbs easier, as you can then really use the larger carbs advanatages...I think, this is pretty much a guess actually, but could be right. :roll:

 

[79gs1000l]

Dink, would the exhaust I have to modify be an aftermarket exhaust for an 1150, or an exhaust for the 1000L frame? I assume that it is for tthe 1150 as the header from the 1000 would be to small,... I think.

Skip, thanks for the engine specs and believe me I can't wait to get the exhaust, and I believe you are correct in my becoming a carb tuning "expert" I haven't got an official E.T. slip but I figure I can adjust all the needles in under 15 minutes, mains in 5 and have carbs out and back in within a half hour. thats pretty good considering it took me 3 or 4 hours to get them in the first time :!: I have an old Hot Rod issue that gives a formula for horsepower based on the weight of your vehicle and driver and your final mph in the 1/4 mile. They rate the accuracy of this test second to the dyno I believe. Maybe I will go find it and post the formula. Also I noticed both Gerry and yourself have 38mm carbs. would 33mm carbs be big enough for the stock displacement. and if I did eventually get a big gore kit, how big could I go with 33mm carbs. Not that I am against getting bigger carbs (obviously) I am just curious.

 

[robinjo]

Hehe... big gore kit :twisted: .

 

[Dink]

Yes I did mean an exhaust to suit the 1150 motor. it may need slight rebending to fit just so.
Dink

 

[79gs1000l]

Thanks Dink, I am going to be looking for a motor and exhaust come spring. If I can convince my wife that the bigger engine means a safer ride,any ideas on how to accomplish this would be greatly apprecciated :!: :twisted:
I found the old hot rod issue and the formula for horspower where the tire meets the ground. it is
HP= (mph / 234)^3 X weight
so in skips case if his rider/bike combo weighs in at 713 lbs he had to have 140 horspower at his wheel. If his combo weighs in at more than 713 pounds his bike has more that 140 hp. (according to the formula) I figure a stock suzuki gs1000L hd 90 horse. If that was at the wheel I should theoretically be able to do 113 in the 1/4 mile, my combo comes in at around 780 pounds. I thought it was a cool formula, maybe some one else will to.

disclaimer( i got these figures the other day, they may be off a bit as I am writing them from memory)

 

[skip]

79 1000gl, Thanks for the formula my bike rider combo is 750 lbs so my hp guess was not that far off.As for the safty thing I would try to convince her that the modified 1000 motor would cost almost as much money to get to the same hp as the 1150 motor is stock. Plus the advantages are relability of a stock 1150 motor is greater than a modified 1000 motor and less chance of leaving you stranded or blowing up.................skip

 

[79gs1000l]

You know skip, according to the formula your friends kawasaki drag bike coming in at 75 lbs lighter than your ride only needed 144 hp to get to 140 mph. TO get to 136 mph your bike had to have 147 hp. Just in case you wanted to brag to your friend abouut the superiority of the suzuki :!:
YOu could say " you know, if you ever want to get to 141 mph you could borrow my motor!" :lol: any way thanks for the advice on how to convince my wife. If horsepower won't convince her, reliability sure might.

 

[Anonymous]

Sorry it took so long here are the carb settings
throttle valve (slide) is 1.5
jet needle is 6DJ30 on middle notch
needle jet (emultion tube) is O-8
main jet is 130
pilot jet is 25
main air jet is 2.0
air screw is 1 turn out

hope this helps this bike does have an open after market exhaust
also I am in south Florida 8 feet above sea level

 

[79gs1000l]

thanks stretracer. thats sounds similar to what i now have. i have the 0-8 needle jet and have in 135 mains but they are a bit rich so when the snow goes away I will change those out for some smaller mains. I don't know what the main air jet does or even where it is I would very much like to see if it is close to the one you found. maybe I can figure it out from the pictures in the carb clean up series. The following is from cope racing about 33mm smoothbores.

For those of you who still own these carburetors a little jetting trick. In order to get better throttle response install 0.6 air correction jets. This allows you to run a smaller main jet while still giving you approximately the same air fuel ratio as before. Good starting point is 4 main jet sizes smaller than you previously had. Also installing a O-6 needle jet will help lean out the mid range.

what is an air correction jet and do you think this is a good idea? and since mikuni no longer makes these carbs where would I get a 0-6 needle jet? none of the motorcycle dealers around here have them.

 

[Anonymous]

Hey 79GS I found a site that might help they have all the info you need
sudco.com