pulls strong and smooth .... until 5000rpm...?

[GelandeStrasse]

Any hints appreciated.
I do have the tiniest weep on the float bowl of #1. It's very slight! I wouldn't think that could cause my issue though. It pulls beautifully up to 5k at which point out won't go any further and feels like fuel starvation across the board. Maybe adjust the float heights?
Thanks in advance.
Btw: motor healthy, carbs spotless etc etc

 

[BassCliff]

Hi,

Some of the usual suspects:

• Float heights
• Main jets too small
• Leaks in air intake system
• Faulty petcock
• In-line fuel filter too restrictive

If it's not any of those then it could be an intermittent igniter, valve timing off by a tooth, etc. Keep us informed.





Thank you for your indulgence,


BassCliff

 

[GelandeStrasse]

Thanks Cliff. Happy to report i can rule out most of the usual suspects in the fuel/intake system. It pulls strong and clean up to that 5k point like it wants to go, but something is holding it back. Is it common to need to adjust the float levels after fitting pod filters and dyno jet stage3? They are currently set a per the specs in my Haynes manual.

 

[GSNewbie]

Plugs

Plugs

Did you remember the rubber plugs? I know, out goes without saying but they are so important...like gas in a car.

 

[AJ]

Thanks Cliff. Happy to report i can rule out most of the usual suspects in the fuel/intake system. It pulls strong and clean up to that 5k point like it wants to go, but something is holding it back. Is it common to need to adjust the float levels after fitting pod filters and dyno jet stage3? They are currently set a per the specs in my Haynes manual.

Ahh, this shows why you need to tell us more when you describe your problem.

I'm taking from the above that the bike USED to run fine, but now you have installed pod filters and a DynoJet Stage 3 kit and it is no longer going above 5KRPM. Is this correct?

Ok, some more questions:
Did you also install a new exhaust or make some other exhaust modification (e.g., punch out the muffler cores)? If you are still running the stock exhaust, then you should set your carbs to the DynoJet Stage 1 (ONE) configuration with the stock needle and smaller main jet (this should be included in your jet kit).

Does this bike have CV or slide type carbs? (sorry, too lazy to look up the 1980 GS1000)

In addition to the above and recommendations already offered by others, I am guessing your pilot circuit is fine, but the problem is the transition from the pilot circuit to the main jets. To fix this, the needles need to be raised to give more fuel with increasing RPM or lowered to give less fuel with increasing RPM. You can test for this very easily:

Make little caps with some paper and tape to partially cover the pod filters. This will cut airflow and richen the mixture at higher RPM.

If things get better and it now revs to higher RPM before bogging, you are too lean, so raise your needles one clip.

If things get worse and it bogs at lower RPM, you are too rich and need to drop your needles a clip.
​

 

[AJ]

Should also add... If the pod filters are new and are the oiled type (e.g., K&N), you may have put too much oil on them and they are choking air flow. This would be the same as putting little paper caps covering up half the filter. The fix is to clean the filters and not drown the element.

 

[Seana23]

Hi all. Ive got exactly the same thing developing on my 850g...
I had lined the tank but it didnt cure properly or ethanol in cheap fuel was melting it off...
So i took it out again and just left the bare metal...
Now, after being fine for a few weeks its started popping and feeling fuel starved at high revs...
This im hoping is crud forming and getting stuck round the fuel filter in the tank...

I wonder if you have the same thing happening...

Xxx

 

[Toasty]

It sounds like an air/fuel issue. Do you have any mods on the bike, 4into exhaust, no airbox lid, pods, etc? You may also have an air leak which is just adding to the lean condition from too small jets (if you have mods) so it just chokes.

Seana, do you have an inline fuel filter? There was one on mine for a while and it was fine for a long time but then it started really feeling fuel starved at higher rpms. I took it off and it helped a lot, I still had to rejet and dip/new oring the carbs though.

 

[GelandeStrasse]

Thanks all the replies
The story is: This was a basket case 1000cc shaftie which I have rebuilt. It did not run before the refurb and it had no airbox so K&N's + Dynojet kit were fitted as a necessity rather than choice. I used the smaller of the stage 3 jetting options because the instructions say if using pod filters that's the way to go. I have a standard exhaust.
So, it starts OK, runs great and pulls strong but won't rev beyond 5k.
The inlet rubbers & Orings are brand new. The carbs have been stripped, cleaned thoroughly, inspected for damage and new Orings fitted. I have not "dipped" the carbs but I have used copious amounts of carb cleaner and left them soaking then rinsed with more cleaner before blowing out all the orifices with high pressure air. The carbs were dry when I pulled them the first time, I believe they had been drained before storage which is good.

I checked the float levels against the hand book and they were in spec. There is a very slight weep from one the the carb bowls. Could be an addition to my problem but I don't think it's the root cause.

Can anyone tell me what the wisdom is for float levels in conjunction with jetting? Is it common to need to adjust the float levels after re-jetting?

The sensation is that of the engine trying to rev but just not getting enough fuel. Like hitting a rev limiter.
Not "bogging", like when the mixture is so off it feels like the motor has lost spark.

Thanks for the input guys!

edit: More details I forgot.....No fuel filter and petcock flowing freely, pods not over oiled....

 

[salty_monk]

Float levels stay the same. With K&N Pods & V&H exhaust I used the bigger of the main jets on 1000G.

I had the same sensation as you on 80 1000G except my "rev limiter" was more like 5500-6k rpm - turned out to be the igniter - I chased Fuelling with it for months before I ran an igniter test & it came back bad!

I used the igniter tests in the Clymer manual...

Installing a Dyna S fixed it.

 

[GelandeStrasse]

Thanks for the info on the float levels and I'll take a look at the igniter box too, it's a likely culprit! At least i can still ride it as is

 

[Nessism]

Try blocking off part of each pod with a sock to see if that helps. Sounds like your mixture could be too lean. Another question is the spark advance. The 1000G engine has a mechanical advance mechanism, but the 1100G did not (the advance curve was in the ignitor). What did you do to the ignition when you performed the conversion?

 

[GelandeStrasse]

Niiiice! I didn't know that. So maybe i have a Mechanical advance and it's seized.
Now i have two non carb related things to check. Wouldn't mind working on something other than the carbs for a change!
Thanks guys
btw: I haven't modified anything on the ignition electrics

 

[Nessism]

Niiiice! I didn't know that. So maybe i have a Mechanical advance and it's seized.
Now i have two non carb related things to check. Wouldn't mind working on something other than the carbs for a change!
Thanks guys
btw: I haven't modified anything on the ignition electrics

As stated above: the 1100 did not have a mechanical advance, the advance curve is built into the ignitor. The 1000 had a mechanical advance, and needs a different ignitor compared to the 1100.

One way or another you need the complete ignition system out of one bike or the other: signal generators, ignitor, and either the advance unit or the rotor.