This might have been answered elsewhere but I can't see it.
I re jetted my k7 gs500e to 142.5/65/20 to suit the new k+n lunch box I fitted. I also replaced all the fuel lines as they were due.
Bike runs fine. Pulls well at town speeds and up to 50/60. However past 60 its real hard going. I get a sort of surging feeling going on similar to when it runs to reserve, but not quite as strong.
Could this be a jet issue? As I've followed what others seem to be using for my setup? Or could it be that the new fuel lines (which were extremely difficult to fit. Seemed tighter than the old ones) are causing a fuel starvation issue?
Start where you modified things.
1. Fuel lines. What size did you use? Stock is 7mm. That's between 1/4 and 5/16 here in the USA. Did you use fuel line made for a motorcycle? Auto fuel line is thicker and prone to kinks. 1/4 might me too small if that is what you used.
2. Fuel and carb hose routing. Be very careful how you route things now. If some hoses are exposed to the wind, it mimics fuel starvation. Search for crosswind engine stumble.
3. Are you sure you turned on your gas tank petcock all the way on?
4. What is your exhaust setup?
Quote from: jestercinti on January 13, 2013, 08:48:44 AM
Start where you modified things.
1. Fuel lines. What size did you use? Stock is 7mm. That's between 1/4 and 5/16 here in the USA. Did you use fuel line made for a motorcycle? Auto fuel line is thicker and prone to kinks. 1/4 might me too small if that is what you used.
2. Fuel and carb hose routing. Be very careful how you route things now. If some hoses are exposed to the wind, it mimics fuel starvation. Search for crosswind engine stumble.
3. Are you sure you turned on your gas tank petcock all the way on?
4. What is your exhaust setup?
Hi,
1. Yes i used 7mm fuel line, however now you mention it the lining is thicker than the old ones, (12mm ish OD), however i cant see any kinks in the pipes, having the lunchbox instead of the stock air filter made more room for them to do what they want maybe?
2. Nothing is pinched on the fuel lines, i just did a search and im going to go check the routing of the carb breather, im not sure where it terminates now that its moved, and the tank vent while im there.
3. yep its in the fully vertical position (if not its v close). i read on here that can mimic the fuel problem as it reduces flow.
4. stock exhaust
thanks for the help, ive got a few things to try now.
I carefully zip tied my carb breather back near the battery on the inside of the frame out of the wind.
My fuel problem at highway speeds all bu disappeared.
Just put the carb breather which was hanging down the bottom of the bike and fed it into the side of the battery box, as there was enough room for it to get in next to the battery without squashing it closed, no change sadly.
did notice however from shining my torch about that my fuel lines are not hanging as free as they were before, as they are pushed up by the breather cover i put on the PAIR boxes intake to cap that off.
So when I get chance to take the tank off I'm going to move that somewhere out of the way, and reroute the hoses and see if that helps.
Just out of interest, from your sig you have the same setup as me, except you have 2.5 turns on the mixture screws, whereas i have 3 turns, would i be best to go to 2.5?
And as you have the same setup as me, what did you do with your PAIR system intake? as I say I've just put a breather filter on it to stop it from sucking up anything (not sure if it needed it but they cost me next to nothing)
Carb mix screws are for idle mostly. But you can try. Hose routing in general is the #1 cause of fuel starvation at highway speeds. Just make sure the breather is not squashed anywhere along the hose including at the source 'T'.
I got rid of the PAIR. Just get block off plates where they enter the engine. It is for emissions only and stands for pulsed secondary air system. Blows air into the exhaust area to further burn unburied gasses.
Thanks for the help.
Tank back off when I can then and check all the routing.
I'll let you know how it goes.
You didn't install an inline fuel filter did you?
Quote from: Twisted on January 13, 2013, 02:46:46 PM
You didn't install an inline fuel filter did you?
Nope, I figured that I didn't want anything getting in the way of the already fussy fuel system lol
did you reset your float levels , you may be getting carburettor flooding or a lean mixture from wrong float levels .this is something you must check when you do a jet change as they are easily knocked also check for air leaks as you have had carbs out.
Quote from: pl4gu3b0rn on January 13, 2013, 03:00:06 PM
Quote from: Twisted on January 13, 2013, 02:46:46 PM
You didn't install an inline fuel filter did you?
Nope, I figured that I didn't want anything getting in the way of the already fussy fuel system lol
Ah, good. They can give you starvation problems if you install the wrong kind.
Any updates?
Not as yet, snows got about a foot and a half of snow infront of the garage at the moment. (which is a lot for englandland)
Here in england, thanks mostly to a lack of preparation. That makes most roads interesting in a car... let alone a bike.
So sadly I cant get it out to go test any of these ideas.
Mini update (however untested) went and did some fiddling and checked float bowl heights, which are ok.
Checked for air leaks too and I appear to have had a small one on the engine to carb boots so I tightened up the clamps and it appeared to go away.
Unfortunately can't give the verdict on if that was the issue as I can't get out at the moment.
As soon as the snow clears off I'll get her out and report back.
Spent the rest of the day clearing our street. Which unusually attracted the help of the neighbours. First time that's happened.... or am I a cynic?
you havnt by any chance put the mid jet #65 in where the main jet #42.5 should be .This has been done before .
Quote from: twinrat on January 22, 2013, 12:02:49 AM
you havnt by any chance put the mid jet #65 in where the main jet #42.5 should be .This has been done before .
nope I took one out at a time and as the size was etched into the existing jets too I swapped the old 130 mains for 142.5 etc.
wouldn't screwing those jets up mean it would run like turd on anything but idle? I only seem to get the issue when I get above 60ish mph and high throttle to try to accelerate?
i tried to replicate the issue at lower speed but still high RPM and throttle (when the snow wasn't here) and i didn't seem to get it. as I was not feeling any stutter in the engine.... and it was taking off very nicely.
rain and high (well comparatively) temperatures forecast at the weekend so this snow should clear up sometime next week and I can get back to trying to work out what's wrong with it.
it looks like you have done everthing right in your rejet and this leaves me with only one other suggestion and that is that you have a massive airleak between your carburettor and your cylinder head I suggest this because i had an old triumph that i took the carburettor off to clean it and right after i did this it would not go over 60 mph with out a lot of surgeing and backfireing .REASON WAS I HADE DROPPED THE O RING OUT FROM THE BACK OF CARB WHERE IT WAS BOLTED TO THE CYLINDER HEAD CREATING A MASSIVE AIR LEAK .yet it ran fine at lower speeds. Go check those carb boots for leaks ,even where they mount to the head ,rubber may be cracked around bolt holes ,or bolts may be to tight making the rubber dish and let air inGood luck
Wahoo.
I just took the bike out after fixing the air leak i found between carbs and engine.
And moving my carb breather up to the battery box.
All is now well. No more fuss at high speed.
Thanks for your help all.
Yay love it when problems get fixed! Now go ride! :thumb:
Right on! Glad it you got it figured.
Not to highjack, but I don't have anything connected to the breather T on the carb, and I routinely go 100mph, with no problems except my head feels like its going to fly off.