2 QUESTIONS

[Tarbash 27]

FIRST, I HAVE A 1979 GS750L, I RECENTLY BOUGHT SOME UNI POD FILTERS FOR IT AND GOT RID OF THE AIRBOX. I HAVE STOCK JETTING AND STOCK EXHAUST. I WOULD LIKE SOME OPINIONS ON WHAT JET SIZES I NEED TO GET AND WHAT JETS. DO I ONLY NEED MAINS? OR DO I NEED AIR JETS AND SLOW JETS TOO?

ALSO, I HAVE SPOKED WHEELS ON MY BIKE. I NOTICED WHEN I JAM ON THE REAR BRAKES, THE WHEEL VERY SLIGHTLY JERKS TO THE RIGHT. I TIGHTENED UP SOME SPOKES THAT I NOTICED WERE A BIT LOOSE. SO NOW I CHECKED JUST ABOUT EVERY SPOKE AND THEY ARE ARE ABOUT THE SAME TIGHTNESS. I CHECKED THEM BY SMACKING A SCREWDRIVER AND LISTENING TO THE TONE OF THE SPOKE VIBRATING AND THERE ALL ABOUT THE SAME. BUT THE WHEEL STILL SEEMS A BIT LOOSE WHEN I NAIL THE BRAKES? DOES THESE HAVE TO BE INSANELY TIGHT OR SOMETHING

 

[LW_Icarus]

the looseness is likely your swing arm bushings if the wheels not real loose. or the axle isn't properly fixed in place. Id start by putting the bike on the center stand and try to move the wheel side to side and see where the play is.

no good input on jets, other than a richer main most likely. someone will come by with advise on that

 

[KEITH KRAUSE]

Not used to re-jetting with the stock exhaust, but maybe 115 mains...raise the needle by installing the jet needle e-clip in the 4th position (second groove from the bottom)...and an additional 1/2 turn out on the pilot fuel screws (underneath)...remove the two float bowl vent lines and leave the ports open...adjust side air screws using the highest rpm method. Be sure ignition timing is correct. Valve clearances must be correct too. Oil the filters with filter oil. Vacuum synch the carbs.
Test the mains at full throttle/read plugs.
Test the jet needles at 1/3 throttle/reads.
Test the pilot circuit at about 35 mph/steady in 4th/5th gear.
The plug reads/performance at each throttle position will tell you what to do with each circuit.

 

[duaneage]

Keep the old airbox just incase you go crazy rejetting.

Check that the wheel is straight in the frame with a puddle of water.
Pour a little water on a flat surface and then push the bike slowely through the puddle and see if your tire tracks are lined up. If not, find out what is up. Could be spacers on the rear or even something bent back there.

If you have a disk brake make sure the rear stabilizer bar is straight, tight and not binding.

Check the rear shocks. Preload should be the same. Make sure you don't have a really bad one that is unloading when you hit the brakes.

 

[gsBert]

you're too rough with your bike tarbash.

i can tell, you type using all caps, and then you speak of jamming on the rear brake.
what do you mean by "jam on the rear brake"? the rear brake is not meant to be used on a motorcycle, or if at all, then really soflty, at low speeds or to hold the bike in place on an incline, but certainly not "jammed on", EVER. i suspect you might be locking your rear tire up...

oh, on the jetting: dont throw out the stock airbox. uni pods dont work with cv carbs... you'll be able to tell when you get a flat spot at 120km/h no matter what engine speed or gear you're in... remember me if thats what you get... (my 750 ran fine after i put the airbox back on)

ah, wait, jetting.... hmmm, run the bike at closed throttle for 15 seconds under minimal load and do a plug chop (kill switch and clutch, coast to stop and pull a plug out, DO NOT LET THE ENGINE RUN at a different throttle setting). that'll tell you if you're lean on the mixture screws (white plug electrode is lean, black is rich, tan is perfect)

repeat at less than 1/8 throttle for the pilot circuit.
repeat at 1/2 throttle for the needle circuit
repeat at full throttle for the main jet

 

[Tarbash 27]

THANKS FOR ALL YOUR SUGGESTIONS. BUT THE REASON I HAVE UNI PODS IS THAT I NEVER HAD THE AIRBOX WHEN I BOUGHT IT FROM THE PREVIOUS OWNER. IT HAD NO FILTERS AT ALL. THE BIKE IS DEFINATELY RUNNING LEAN. AIR SCREWS HAVE TO BE ALL THE WAY IN OR THE BIKE WONT RUN. HAS TO BE ON CHOKE EVERY TIME TO GET IT FIRED UP. EVEN WHEN ITS HOT. AS FOR THE WHEEL. IT HAS TO BE WITH THE SPOKES. I HAD A MAG ON BEFORE THAT WITH NO PROBLEMS. WHEN I MEAN JAM I N THE BRAKES I MEAN HIT THEM GOOD ENOUGH WHERE IT SHOULD SLOW YOU DOWN TO STOP. NOT SO HARD WHERE IT WOULD SKID. I USE THE REAR BRAKES FOR MOST OF MY STOPPING. AND I ONLY TRY TO USE THE FRONT IF I HAVE TO REALLY STOP QUICK.

 

[KGB]

If it's that lean, the motor will desrtruct VERY soon.
Either by putting a hole, due to it melting, in the piston or the rings will destruct.
Get it jetted before you continue riding it, or an air box.

As to not using the front brake.....about 70-80% of your brake force come front using the front brake.
Both brakes together will gice you the most effective way to stop.
If you're unsure of how to brake, take the MSF course.
NY offers classes all over the state
www.msf-usa.org and search for your area.

 

[gsBert]

tarbash: there is a key on the left side of the keyboard, it says "CAPS LOCK", press it please, it's really annoying when people type in all caps...

(ThIs Is OnLy sLiGtHlY WoRsE)

if you use the rear brake for most of your stopping you dont know how to ride and dont deserve a gs...
i'd hate to see your stopping distances....

my rear brake master cylinder emptied once (wrong routing on hose)
i only found out when i tried to use it to keep my bike there on the downhill to my garage while fumbling for the remote. i dont know how long it wasnt working, i tested it before leaving as usual, but then it was a 10 hour ride, and that's the first time i used the rear brake... (my rear brake pads last forever, i've never had to change any yet)

im not gonna reply to you if you type in caps... i told you the truth about the jetting in my first post, now go take a motorcycling course please...

 

[Tarbash 27]

ok, i dont know how this was brought up in this subject that using the rear brakes makes me a bad rider. i just prefer to use them and the are more comfortable for me when im riding. i know how to ride a motorcycle. i work for harley davidson and i ride bikes all day long. but im not really harley fan. i love my gs's. i have riden motorcycles that were not even manufactured with front brakes. so dont tell me that your only suppose to use front brakes. all i wanted to know was is there a problem with my rear wheel. and some jetting problems i had. i put over 2000 miles on my gs running like this. its my only form of transportation as of now. thats why i want to get it fixed soon. so instead of yelling at me. i just wanted to get some info from some other gs'ers

 

[mixongw]

tarbash: there is a key on the left side of the keyboard, it says "CAPS LOCK", press it please, it's really annoying when people type in all caps...

(ThIs Is OnLy sLiGtHlY WoRsE)

if you use the rear brake for most of your stopping you dont know how to ride and dont deserve a gs...
i'd hate to see your stopping distances....

my rear brake master cylinder emptied once (wrong routing on hose)
i only found out when i tried to use it to keep my bike there on the downhill to my garage while fumbling for the remote. i dont know how long it wasnt working, i tested it before leaving as usual, but then it was a 10 hour ride, and that's the first time i used the rear brake... (my rear brake pads last forever, i've never had to change any yet)

im not gonna reply to you if you type in caps... i told you the truth about the jetting in my first post, now go take a motorcycling course please...

Sombody pee in your Wheaties this morning?

 

[duaneage]

if you use the rear brake for most of your stopping you dont know how to ride and dont deserve a gs...
...

i sURE aM gLAD yOU dON'T wORK fOR tHE dMV oR aDMINISTER tHE gSREOURCES, iT WOULD bE HARDER tO gET tAGS AND wE wOULD nOT hAVE aNYWHERE tO cOMPLAIN aBOUT IT

Cut him some slack, bert, Tarbash's Capitalized Emails are a bit loud but they are distinctive. Deciding what brake to prefer does not draw a line on riding ability. Not hitting the ground is a far better indicator.

Besides, he might have an answer to a problem you have someday and decide not to share it.

 

[KEITH KRAUSE]

Tarbash, the "caps" thing is something I also did my first few posts.
I was a newbie and didn't know about computer etiquette. Caps are considered yelling and the editors here actually punished me by deleting my first few posts. It is a little harder to read the caps. So much for that.
As for gsBert's jetting comments about Uni's not working with CV carbs, that's not a problem because your '79 uses the easier to tune VM slide carbs.
I believe my post about how to re-jet your bike will get you started off well. Jetting is trial and error and it can take time, so be aware. It's more than just choosing jet sizes. The basics, such as ignition timing/quality spark, valve clearances, compression, clean carbs, etc, all effect the re-jet. Consider a stock air box.
As for your rear wheel problem, I'm not quite sure what's happening. You say the wheel feels like it cocks to the right under braking. Do you mean the front/forward part of the tire actually points to the right? You can see the axle/adjuster move? First thing I can think of is to properly torque all hardware and see what happens. Bike should be on centerstand. Carefully re-align the axle and adjust the chain for about 1" of slack at the mid-point of the front and rear sprockets. Be sure the chain adjuster bolts are straight and their ends are seated in the depressions in the chain adjuster blocks that bolt into the swingarm ends. Torque the nuts that hold the chain adjuster bolts firmly. Torque the brake arm bolts. Be sure they're seated/installed correctly. I'm not sure about their proper torque and hope you have a manual. Somewhere around 20 ft/lb is probably close for the brake arm bolts. Torque the rear axle nut to about 72-75 ft/lb.

 

[gsBert]

ok, i apologise for ripping on you man...

yeah, as a matter of fact, my wheetabix got peed on this morning, weather report calls for rain tomorrow, my only day off....

see my first post on jetting, where i describe how to do a plug chop. doing this will tell you everything you need to know about your jetting.

as far as your rear wheel (i do wish youd use the front brake more though): just to be absolutely sure you're not locking it up (you might without knowing it, and in any case, it'll help you diagnose stuff...), do this:

ride at around 70 km/h, hit the clutch and the kill switch (as for a plug chop, hey, do a plug chop at the same time), coast for a while to get familiar with the sounds your bike is making...
now gently apply a bit of rear brake, did it make a clacking sound?
does it clack if you apply more firmly (still without locking the tire)?

check the rear torque arm for the caliper... and the rear wheel bearing (how old is it?)

you know what rear wheel dampers are right? do you have all of them in there? that could do it, or at least feel like it... on second thought, no you'd feel that when shifting gears (unless of course you use a clutch to shift)

oh duanage: i resent that comment, lol. if i worked for the dmv (trust me i wouldnt want to), the roads would be a lot safer. up here in quebec they're talking about increasing the m/c license plate to 1000$ because ppl die too much, truth is they dont need more money to stay safe, they need to know how to brake and countersteer (and more importantly to how to look, im not talking fashion here)

the reason im a big front brake advocate is when you brake you transfer weight forward (away from the rear tire) this increases front traction and therefore brake-ability in the front while unloading the rear tire (especially in a hurry) makes it easier to lock it up.
people who realise they locked up a rear wheel tend to let go of the rear brake, the tire that was passing the driver then grabs traction and causes a high-side...

if i worked at the dmv, the driving exam would have 400 or so questions on the physics of driving, and yeah, a lot of people would fail that and not get their suicide permit...

my preference when braking isnt front or rear biased, i'm more in favor of generating a lot of heat real fast (brakes are entropy generators)

 

[Tarbash 27]

WELL I GOT MOST OF THE INFORMATION ABOUT REJETTING THAT I WANTED AND WILL TAKE IT INTO CONSIDERATION THIS WEEKEND. AS FOR THE WHEEL. I USE TO HAVE STOCK MAGS ON THE BIKE. WHEELS HAD NO PROBLEMS BRAKING OR ACCELERATION. oops, i didn't realize to now that i was in capitals. Anyways i bought some spoked wheels off ebay that i liked. they went on with no problem. the bearings were good. the first trip down the road i tested the front and rear brakes with the wheels. front was fine. the rear i noticed would slightly jerk the bike to the left. which was the wheel angleing to the right a hair. so i was cruising steady at a higher rpm than punched it full throttle to see what the wheel does. while accelaerating like this, the wheel went the other way. so i went home. noticed that not all the spokes were tight. so i figured it was the play in the spokes. whereas the hub stays still but the actual rim itself moves from the loose spokes. so i brought the bike to work at harley-davidson. put the the bike on its centerstand and trued the wheel and tightened some spokes with a spoke wrench. now they all seem evenly tightened. so i went to check the rear wheel again by hitting the rear brakes. there is still a slight jerk in the wheel. not as bad as when i first got them. this is just what i wanted to know. do the spokes have to be really tight. at home i was using a wrench to tighen the spokes and the little wrench broke. luckily its craftsman

 

[duaneage]

Check the dish on the rear wheel and compare it to the cast wheel

Dish refers to making sure the rim is centered over the hub, check it in the same place on each side by placing the rim standing up on a floor next to a wall. Measure from the rim to the wall then reverse the wheel and check the other side. Rotate the wheel 180 degrees and repeat. Mark the wheel with tape so you check it at the same place. Placing a level against the tire ensures it is parallel with the wall.

Now compare the measurements to your cast wheels which are fixed dish. IF the spoke wheel has different dish than the casties you need to either adjust the rim through the spokes to correct it ( not really possible) or else shim the wheel enough to compensate.


i have a wheel dishing tool I use for my bicycle wheels. It is amazing how many bicycle tools come in handy on a GS. Especially headset tools.

 

[Tarbash 27]

OK, I CAN ORDER JETS THROUHG MY JOB AT A $1 A PIECE. I DONT FEEL LIKE TAKING THE CARBS OFF YET. ARE THE MAIN JETS HEX SHAPED OR ROUND. I CANT REMEMBER. SO I CAN ORDER THEM FOR VM26

 

[Hoomgar]

Depends on manufacture. All the jets in my two sets of VM26 carbs though were round.