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Bogging at low speeds

  • Thread starter Thread starter DrImodium
  • Start date Start date
D

DrImodium

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I bought a 80 GS1000 two months ago and finally took my first ride yesterday. Under load and at low speeds, the bike is bogging badly. Once you get up in RPM's it runs great but it wants to fall on its face when I first pull away from the curb and right after every shift. It has stock pipes and pod filters that the PO put on. When he put them on he said he said he synced them but Im not sure if he jetted the carbs. Im not 100% sure it is the carbs, from my research it could also be an electrical issue. What should I check to try and narrow down the cause of the bogging?

edit: I have searched. This is the first bike that I am maintaining myself so Im not really sure what I should be looking for.
 
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Mac..from what i have read and understand, the CV carbs are harder to get to run properly with pods. Since that year bike is "supposed to have" VM carbs the pods should function relatively well..I didnt see he had posted what type he has on her. I never assume that a PO has done anything. I would redo the carbs to be sure they are correct and then have them synced again. sounds to me like theres possibly some blockage in the idle circuit or the fuel mixture screws.. just my guess anyways.
 
1st thing I would do is all those things that an old bike requires:

Valve adjust
Carb clean
clean electrical connections

(I know there's an actual list somewhere)

Then, I'd find a stock airbox and put that on - pods without a pipe are fairly useless, and you can get a K&N drop in filter that lasts forever (well, 28 years for mine)

I bet if you pull the carbs, the jetting is still stock. A definite case of PO syndrome, better check everything.

As for your problem, it could be jetting, it could be the pilot jets are clogged, the screws may be set god knows where

Chuck, a 79 has VM carbs
 
Pop a float bowl off and see what jets are in there. The #1 float bowl is easy to do with the carbs on the bike.
If it's a 95, he didn't do anything as far as jetting, 95 is stock. I would guess you would need around a 110 or 112.5, but that's purely a guess. 95, the stock main jet size is not going to work with pods.

Better yet, take the carbs off and look at everything, replace the O rings, all of it. With pods it should be easy enough to get the whole works off.
 
Mac.i know that it should have VMs..but what does this bike have on it?? Someone could have slapped a pair of CVs on it as well...Who knows..I reread it and didnt see a reference to the type of carbs he has..just sayin
 
reference to previous post...I got a 750 parts bike that the dude had CVs on it when it should have had VM26s..who knows what previous people had done..also the bike we got for my buddy Scot last fall ( 78 750 E ) had VM 29s on it..
 
chuck hahn said:
reference to previous post...I got a 750 parts bike that the dude had CVs on it when it should have had VM26s..who knows what previous people had done..also the bike we got for my buddy Scot last fall ( 78 750 E ) had VM 29s on it..
Click to expand...

Chuck,

That does fall into the PO syndrome, so DR I, give us some pics!
 
I agree, pics would be helpful. If only to find out which type of carbs are on the bike in question.

If the P.O. sync'd them, it does not mean that they are running the right Air to Fuel Ratio, it just means that they are equally pulling more air than stock across all cylinders.

I am not trying to start something here, but I was under the impression that putting pod filters on any type of carb will flow more air than a stock airbox setup, thus requiring jetting to get them to run right.

In my experience, it is possible to "tune" pod filters to a certain extent by limiting the volume of air they can flow to get them closer to stock. A rejet may still be required since they may not flow the same amount of air at a given throttle opening as a stock filter would due to the difference in the filter element material.

Correct me if I am mistaken, but unless the carbs (VM or CV) have already been rejetted, or the pod filters are K&N cotton material type designed to emulate the stock flow rates, a rejetting will be required to cure a lean condition due to a higher rate of air flow?
 
THe biggest problem with pods on a CV carb is the fact that a C-onstant V-elocity of air is required to blow into the inlet tube to properly accuate the slide diaphrams..Most pods dont have built in velocity stacks to make a strong enough and even flow of air coming into the carbs..thererfore the slides flutter all over the place, dont open in sync ( or at all ) and you just cant tune the carbs under such conditions.. Vms on the other hand are mechanically limked to the throttle rail and dont suffer from pods. I have seen guys open the ends of pods and put a small piece of PVC pipe inside and then reglue the ends on to make home made velocity stacks. I have heard mention of some pod manufacturers that do, put built in velocity stacks in. Best bet is that if you have CV carbs avoid pods at all cost..just my 2 cents worth ..
 
The carbs that are currently on the bike are CV carbs. I called Z1 and talked to them for a little bit yesterday and they told me to try and shim the needles and that it should take care of the problem. That advice didnt really make sense to be since shimming them makes them richer but I was under the assumption that bogging at low speeds was due to it being to rich? Do I have my info backwards?
 
DrImodium said:
Do I have my info backwards?
Click to expand...
I don't know if you have your information backwards, but I am getting conflicting information here. :-k

In your opening post, you say you got a '79 1000. Your sig says you have an '80 1000. One bike? Two bikes? Which one are you working on?

Bogging at low speed simply means that the engine is not getting enough of a proper air mixture. Could be rich, could be lean, could simply be not enough.

Shimming the needles will help more in the mid-throttle range. The pilot circuit is what is in use at idle and low-throttle openings. How far out are your mixture screws? After the carbs have been properly cleaned and re-o-ringed, most of us set the screws about three turns out, then tweak for best running when the engine is warmed up. If you are still somewhere near the stock setting of about 1 1/4 to 1 1/2 turns, that could be the source of your bogging.

If you choose to shim the needles, please do it properly. Some guys have simply iserted shims (washers) between the spring and the clip, but that is not correct. There is a thick nylon spacer above the clip, at the top of the needle. Match its height with a stack of washers, then cut it in half and use the washers instead of the nylon spacer. The spring pushes the needle up to the top of its "home". Reducing the thickness of the spacer allows the needle to go higher, richening the mixture. Adding washers between the spring and the clip only increases pressure on the clip, it does nothing to change the position.

.
 
Edited the original post. Bike is a 1980 GS1000. Screw are set at factory settings. Tomorrow Ill try adjusting them. In order to remove the plugs put in from the factory, do I have to remove the carbs to gain access to the plugs so I can remove them? To me it seems like an obvious "yes" but ya'll are the experts.
 
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