'79 gs1000e resurrection bogs and hesitates under load

[garyS-NJ]

crap, wrote this nice post and went ot look at something before submitting and got logged out.

I need to decide attack the carbs, or swap the dyna 2-3 in place of the old points ignition.

so briefly, I just got this bike that last ran in 1995. stored with 2 stroke oil and maybe stabilizer in the gas. cleaned plugs, checked spark, fresh oil drained fuel and ran some fresh fuel through 3 carbs (#4 drain screw stripped) and she runs. a little rough so I did a light sand on the points contacts and figure I'd put 20 highway miles on with heavy seafoam.. She idles and revs without hesitation but dumping the clutch I have to get on the gas else she's boggy. And she isn't smooth and lacks power (with and without the muffler). she had rotted intake pods so I installed new oval pods I had laying around for my '78 cb750F and she has a home made 4:1 header (with home made can muffler but that's off for now)..

guess I'll flush the gas tank and check the petcock (does the petcock have a strainer?). and check for intake leaks, put in new plugs and ohm out the plug caps (and ohm the coils too but she does have good spark). But then I'm thinking rip the carbs before touching ignition. can anyone point me to recommended jetting for pods and open header? Also, has anyone seen bad condensers or timing do this?? (I always saw bad ignition would affect reving in neutral (just like bad carbs). Everything I read has bog and hesitation under load as a carbs lean problem..

 

[Big T]

The condensors are bad at that age. Get a Dyna S

Also,totally strip and clean the carbs per the tutorial.

Check what your jetting is now and report back. Most find 122.5 and needle raised up a notch to be a starting point

You're trying to short cut. Check the Top 10 Newbie mistakes and cover all of those steps for a better result.

 

[garyS-NJ]

ok, quick test here at night and see my points are barely arcing. and some carb cleaner spritz at the intakes indicates 1, 2, & 4 leaking at the head (not at connection boot to carb). looks like a gasket between the intake boot and the head but I can't find a gasket or oring seal on partzilla.. help?>? and should I use hi temp silicone (I know a bear to get apart but it helped seal orings on my xj Yamaha). also on the carbs (forgive me because I'm asking without reading anything about old suzis..), there is three nipples on carbs which looks like on is vacuum to petcock and the other two just route down near the swingarm. open, not plugged tubes? can this be intake vacuum open?? and on this line, on the head intake ports, I see allen screws which I'm guessing are plugs for nipples to sync the carbs. anyone know where to get the nipples? (I'll do a bench sync and probably be happy but just in case). and again, on the carbs, can anyone recommend upjet sizes for pods and open header? for my '83 xj550, I used factory Pro website and perhaps an Xj forum to get the jet sizes and then studies Yamaha part numbering to order the jets by part number (not oem for my xj550). I know I could pay stupid money for someone to send me a set of jets to try but I'd rather just buy the jets by P/N and save a buck. Lastly, I got a '77 gs750 also and the carb sliders are frozen. I got an extra set of carbs with that bike and they look same except for the idle stop screw but is there a way to identify carbs for each bike? I don't see any numbers on the carbs. might those same carbs fit my GS1000E?? with different jets?? (I recall the gs 1000 is a stroked gs750 so maybe intake ports same? sorry in advance for the dumb questions here.

 

[garyS-NJ]

The condensors are bad at that age. Get a Dyna S

Also,totally strip and clean the carbs per the tutorial.

Check what your jetting is now and report back. Most find 122.5 and needle raised up a notch to be a starting point

You're trying to short cut. Check the Top 10 Newbie mistakes and cover all of those steps for a better result.

thanks, I'll look for those newbie mistakes. I always say anyone can do it with tools tho and I AM trying to shortcut right to riding this bike asap. (but I do have two other bikes on the road)/ I'm sure like a gazillion folks here have rejetted for pods and open header so jet p/N's shouldn't be too hard. that 122.5 main is stock or for pods and open header? and what about the pilot jet? and raising the needle is then leaning it?? I'll poke around here but hoped there was a general set up for pods and pipes.. And believe it or not, the points are barely arcing (I'm 54 and seen points arc since I'm 10...). I do have the dyna 2-3 to install but figured since the points seem to be working good and the carbs are definitely leaking, might be better to attack the carbs without throwing in another variable. I put a dyna in my '78 cb750 and it started and idled smoother and ran nice.

 

[steve murdoch]

You are right to limit the variables and also right to look at the carbs first.
A set of carb and manifold o-rings are recommended as well.
Cleaning how-to here: http://members.dslextreme.com/users/bikecliff/images/vm_carb_rebuild.pdf

 

[garyS-NJ]

before I yanked the carbs I verified that it was leaking at the manifold O-rings so two sets of them are on order (I have a '77 gs750 to resurrect also). I'm cleaning two sets of carbs for the 750 and will get to the gs1000 carbs next. On the first set of 750 carbs I noticed that the parts list item 12 needle assy has a solid metal needle and also solid metal seat with no oring to seal against the needle tip. All my previous experience with carb bowl fuel fills has either a metal seat and Viton tipped needle or a metal needle with a tiny oring seated in the seat. can this be right? (metal needle against a metal seat??). thanks on above starting point for re-jetting the gs1000 for pods and open pipes. go up to a 122 main and shim the needle. I'll hunt around for the needle shim procedure. Is there a recommended change for the pilot jet? also is there a recommended starting point for the mixture screws (one under the bowl and one on carb side). I checked the mixture screw settings on carbs 3 & 4 for the first set of 750 carbs but they were not the same so I'm guessing someone was playing with the 750 and it came from the same owner as the gs1000 so the gs1000 may well be screwy. The 750 has pods and stock exhaust with 100 main jets and 15 pilots (stock?) but I want to get a 4:1 exhaust as the oem is horribly rusted anyway).

 

[Big T]

Needles on VMs don't need to be shimmed

They have a series of preset position, you just move theE clip
pilot- stock 15
Fuel screw -7/8 -1 turn out
Air screw - 2 turns out

 

[garyS-NJ]

pilot jetting for pods and 4:1 open header

pilot jetting for pods and 4:1 open header

Needles on VMs don't need to be shimmed

They have a series of preset position, you just move theE clip
pilot- stock 15
Fuel screw -7/8 -1 turn out
Air screw - 2 turns out

thanks on that Big T. I assume above was for the '77 gs750.. the one set I took apart yesterday had the fuel screws set at 1 & 1/4 on the outside cylinders and 1&1/8 on the inside cylinders..

looking at the P/L item 21 for the '77 gs750, I see two pilot jets listed and I had a #15 in both sets of carbs I opened yesterday.. but then for the '79 GS1000 I see only the #15 pilot listed. Both bikes will be fitted with pods and open 4:1. I have advice above for the GS1000 to go from a #95 oem main to a 122.5 main and one notch on the needle but no pilot jet change (stays the #15). Interesting to me that the '77 GS750 and '79 GS1000 use the same carb bodies yet the parts list indicates the gs1000 gets the smaller #95 main jet and the GS750 gets the larger #100 main jet

can you advise on rejetting the '77 GS 750 for pods and open 4:1 exhaust??

gs750 P/L:
21 [h=2]JET, PILOT | B,C&EC; #15[/h]09492-15005



21
[h=2]JET, PILOT (22.5) | B; #22.5 MARK in.45010in.[/h]09492-22008



'79 GS1000 P/L:
21
[h=2]JET, PILOT | #15[/h]09492-15005

 

[garyS-NJ]

happy me, got the 750 fired up last night. I went through a spare set of carbs (which I left a buggered mixture screw in) and with a sticky float needle, I cleaned the needle, seat, and adjusted float height. whoops no spark? and no voltage at points or coils: off/run switch cleaned. still no spark? filed points. and got sparky. with no airbox, I installed a set of pods I had for my cb750 and she fired up. almost respectable but I forgot to plug the vacuum line for petcock.. points were arcing pretty bad. but she's gonna live.

 

[garyS-NJ]

Got my intake manifold o rings and stainless Allen bolts. Loosed the old ones with an impact driver and opened the carbs up. They look grungy outside but spotless inside with 112.5 mains and #20 pilots. I don't yet know how to check the needle clip height but I'm inclined to replace the intake o rings and give them a cleaning. Looking down the throats with a guitar string bench sync shows they are pretty close. Ill just record and reset mixture screws same if they are reasonable. All in all the carb set looks pretty good and the intake o ring leaks were small so I'm inclined to think the running under load issue was ignition. So ill retry with the intake o rings and then swap in a set of new condensers before changing in the Dyna ignition.