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Brrrr.... pop POP POP bbbrrrRRRRRRbBBbrrrrrr POP POP POP

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This is about all I get above 4000RPM on my 77-79 gs1000. Here's a little history, I recently bought the bike as a 78gs750E, but knew that's not what it was, seeing as how the engine was clearly an 8-valve gs1000 motor. The carbs are 28 MM BS carbs, the stock ones off ofthe 78 750. I opened the bottom and found a #15 pilot, 100 main. It has Pod UNI foam filters and a 4-1 from V&H. I read somewhere that with pods you need to go up 2 sizes in the main, and as I understand it the 79 gs1000 had 95 mains, making the 100 two sizes up, but I have nothing on the top end. I'm also going to need coils soon, any one know where I can get CHEAP coils? I read another post and it souunded like I should be running something more along the lines of a 142 main. I don't want to pay a crapload for a jet kit, these are the stock 79 1000 cams, so I don't think I can degree them, it has an inductive pickups (older electronic Dyna(?)ignition). It's definately running lean and I need a place to start fixing it... 70 on the freeway is dangerously slow. Also, where can I find stock (not heavy duty) clutch springs for this, this clutch has Heavy duty springs, and it's so tight that the lever attaching to the spindle will slip a little at a stop light sometimes, disengaging the clutch and causing me to stop and readjust the cable. Thanks, ~Ben
 
As for jetting,I go with Dynojet. But using the Mikuni jets I would go up to 115 or 120's and test. I would also raise the jet-needle 2 notches and test,
if the needles are in stock positions. You don't need to change the pilot-jet. If you have any problems at idle/low rpm,such as 'spitting' out the filters,turning the side air-screw about 1 turn out from bottomed should help,then re-set idle. You can set cam timing if you buy slotted cam sprockets,or file out the existing holes. You can get standard clutch springs at any dealer/parts store. As for the popping above 4000 rpm, I would suspect the points(if it still has them)and coils. It's also possible the carburetion is too rich due to dirty filters or carb passages blocked. KK.
 
More info:

More info:

Here's a little more info I gathered from my short ride today:
When cold with choke on she's a dog out of the hole, and I mean a big ole fat st. bernard that's been tranquilized. then at 3500 or so she starts to pull strong up until 5500, then a brick wall. Nothing. Nada. No power. Thus, I suspect the main. but why so sluggish out of the hole? I haven't had this bike long, and it's definately in need of some serious help, so, uhh.... HELP! Thanks ~Ben
 
Your idle is probably running a bit rich as well, I've just been working on the same problem with my bike, try loosening the air screws.
 
HMM, the 1000 comes on the cam around 5500 to 6000, and you say you need coils?
is it posible your spark may be cutting out when it starts to come onto the cam?
I have seen a cbr600 do something very similar, it had a bad ignitor box.
 
Okay, I pulled the plugs, and now I'm thouroughly confused. The plugs are new (only 20-25 miles on them) only used for light in the city trips, and I didn't think this color was possible. The porcelain around the electrode and the electrode are midnight black. (Maybe a rich idle? maybe caused by running with choke about 25 percent of the running since the plugs were installed?) That's fine, a rich condition, but the probe, or the flange, or the little metal thing that hangs over the electrode is WHITE! BRIGHT BRIGHT WHITE! Darn near luminescent. I do think the coils need replacing, but my checkbook is a little light this month, so unless my wallet gets replaced, it'll be a little while and I want to be certain before I drop 120 dollars on accel coils. I can't afford a jet kit, so I'll order Mikuni Jets from DK, but I don't wanna take the trip if this isn't the problem either. It's rare that I have to admit this about something mechanical, but I'm confused :oops: ... HELP Thank you, ~Ben
 
This is a total shot in the dark, but is the gap set right on the plugs? I have no idea if that would cause it, but may be worth checking.
 
I would also replace the carbs. The stockers are 26mm. The 750 carbs may be nothing but trouble if you not an expert at jetting. I know you don't want to hear this but trying to make an engine run right,using carbs
designed for a different engine,can be hopeless.
 
KEITH KRAUSE said:
I would also replace the carbs. The stockers are 26mm. The 750 carbs may be nothing but trouble if you not an expert at jetting. I know you don't want to hear this but trying to make an engine run right,using carbs
designed for a different engine,can be hopeless.
Click to expand...

My bike has the 28mm carbs as stock instead of the 26mm ones, so in theory if it is the same type (VM28SS) he could get it running right, mine is completely stock with the airbox, filter and 4-2 exhaust so I can't be of help with the jet settings.

If I remember correctly the 750's I owned, a '78 and a '79 2-valve model both had 26mm carbs. Maybe he's got an "S" engine and carbs.
 
Maybe they are 26mm, I was pretty sure the 78 GS 750E came with 28s but I could be wrong... they're a pain to get into the intake boots, so they seem a little oversized. Getting a whole new rack of carbs to tune for this bike is out of the question. Money is tight, I'm not gonna drop 150 on a set carbs that won't even be tuned yet. I'll work and rework the ones I have all that I need, but I cannot afford to buy parts and parts and parts... I'm aware that I can get a set on ebay for as little as 20 dollars, but usually they need serious work to get to the point where I could START to tune them... I'm still thinking the main is too small, will raising the needle affect the idle? this bike is acting funny, some days it pulls good out of the hole, most days it's fat out of the whole and then strong for a little bit then dead. really nothing about 5500rpm, except a lean backfire
 
Don't screw around with Accel. I don't have much experience with bikes but a lot with cars, Accel makes crap ignition and injection parts and puts a chrome finish on the plastic to make you think its special.

In the car world it's MSD, I have no idea what good stuff for GS's is.
 
Allthough some will not agree,I have learned through trial and error that the needle will have some''overlap'' effect on the pilot circuit(idle.) The needle is supposed to start working at about 1/4 throttle,but my bike was ''spitting'' at idle and raising the needle helped a lot. I did not raise the needle because of the spitting,it was just a bonus I got while re-jetting my mid-range. Turning in the side air screw a turn eliminated the rest of the spitting. As for coils,I have the Dyna's and they work well.
As for pilot circuit adjustments, it's hard to say because of the possible carb size problem. My 26 stockers are set at : pilots (underneath) 1 1/4 out, side air screws 1 turn out,and the stock #15 pilot jet. I have the K/N ovals and a V/H 4-1 pipe. Runs great.
 
I don't know if this is any help but my bike, a GS1000 running stock carbs and filters with a micron exhaust, was doing exactly the same thing. i changed the plugs and when i took the carbs off (what abloody nightmare job) one of the main jets and one of the pilot jets were lying in bottom of the float bowl. hope this helps. jeff
 
Definitely go with the Dyna coils over the Accels, in my humble opinion they are twice the coil for about the same price.
Doze.
PS. I have a set of Dyna's on my 1150 and they have worked flawlessly.
 
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