Anybody here have a tips what to do next?
Bike has these parts
-K&N lunchbox
-Some aftermarket exhaust, maybe vance&hines. Don't know for sure.
- Petcock have been changed to normal valve
Best way to cold start my bike is 50% choke, 100% too much and 0% too less.
I basically can drive with the bike but fastest way to accelerate is about 50% throttle use until 5-6k rpm, then i can use 100% throttle, if i pull throttle 100% open under 5k, bike won't rev up (i have tried main jets of 135, 140, 145, 150. No difference)
- if i do like 500m little test drive and engine warms up a little, i can't get it to idle anymore, with or without choke. I have to keep it on with throttle. If i raise the throttle stop screw idle starts to hover too high.
Things done to the bike. (did not start when i bought it)
- Both intake valves have been changed (old ones were bent)
- Valve clearances have been set
- Carbs have been cleaned and all o-rings and needles etc. have been changed to new from repair kit i bought.
- Carbs are synced
- Changed intake boots, because old ones were cracked.
I don't have any more ideas. Anybody else have same type of problem?
Please let me know if i can add more information for troubleshoot.
Quote from: RReTo on February 25, 2022, 11:45:28 PM
Bike has these parts
-K&N lunchbox
-Some aftermarket exhaust, maybe vance&hines. Don't know for sure.
This will make it harder to troubleshoot. Someone will be along soon enough to tell you it will run great with these parts.
Quote
Best way to cold start my bike is 50% choke, 100% too much and 0% too less.
50% choke required to start means it's way too rich on pilot. You should need 100% choke to cold start.
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I basically can drive with the bike but fastest way to accelerate is about 50% throttle use until 5-6k rpm, then i can use 100% throttle, if i pull throttle 100% open under 5k, bike won't rev up (i have tried main jets of 135, 140, 145, 150. No difference)
There's no difference in all of those main jets because the bike is not running on the main jet at under 5k rpm.
I think it's too rich on pilot. But one way or the other, pilot circuit is screwed up.
Quote
- if i do like 500m little test drive and engine warms up a little, i can't get it to idle anymore, with or without choke. I have to keep it on with throttle. If i raise the throttle stop screw idle starts to hover too high.
Set the idle mixture according to the procedure in my blog post (my signature below).
Hopefully someone will tell you what main jets it needs for lunchbox and this unknown exhaust. But the problems you are having are not the main jet, they are pilot jet. You'll get brand new problems once you fix the pilot jetting.
So. What size pilot jets are in there? Or better yet, why not just yank the carbs again and verify they are 40, and also make 1000% sure you replaced the pilot needle o-rings, since if they are old and hard then it will run terrifically rich on pilot no matter what the jetting or pilot screw setting. I'd go ahead and put fresh new 40 pilot jets in it and replace (again) the pilot needle o-ring, just to be absolutely sure it's not leaking.
Thanks!
I did change the o rings under idle mixture screws but when i
now checked them, they were ripped. Have to change them again and try if it helps.
Pilot jets were 40, i checked them also.
Quote from: RReTo on February 25, 2022, 11:45:28 PM
Anybody here have a tips what to do next?
Please let me know if i can add more information for troubleshoot.
Hello Berto......its been a while :thumb:
Have you considered the plastic carb sides and guides? They don't last forever. They are moving parts and as such will eventually wear and when thy do go they tend to take the emulsion tubes and needles with them. Upshot of a worn tube is generally a rich mixture at low rpm and this appears to be symptomatic with the conditions you are describing.
At the age your carbs are at you have to accept its highly likely there will be significant wear present. This worn slide condition is very rarely if at all mentioned when people in this forum talk about Mikuni/GS500 carb issues and what complicates things further is the fact replacements are not available directly from Suzuki. You need to source them from carb` specialists.
I suggest your next move is to take a good look at the condition of your slides and emulsion tubes, if only to rule them out. These articles will help https://store.moto-lab.com/articles/bst40-slide-guide-wear-indicators. https://store.moto-lab.com/articles/emulsion-tube-inspection-guidelines
I appreciate you are not in the UK but I have bought replacements from here in the past https://nrp-carbs.co.uk/shop/index.php?route=product/product&manufacturer_id=25&product_id=5770.
EDIT....I have just noticed you are not actually Berto, apologies for the confusion :icon_eek:
QuoteEDIT....I have just noticed you are not actually Berto, apologies for the confusion :icon_eek:
Yep, not Berto but appreciate the help :thumb:
Have to check those as well. Thanks!
Quote from: RReTo on February 25, 2022, 11:45:28 PM
I basically can drive with the bike but fastest way to accelerate is about 50% throttle use until 5-6k rpm, then i can use 100% throttle, if i pull throttle 100% open under 5k, bike won't rev up (i have tried main jets of 135, 140, 145, 150. No difference)
- if i do like 500m little test drive and engine warms up a little, i can't get it to idle anymore, with or without choke. I have to keep it on with throttle. If i raise the throttle stop screw idle starts to hover too high.
That 50% throttle till 5-6K, if you go 100% it falls on its face = Slide coming up too fast. You should train yourself to open throttle just fast enough, but K&N also supplied plugs to plug holes in the slide. IMHO, an excellent way to destroy a $$$ and unobtanium part.
Idle getting too low and stalling when warm is a sign its rich, likely caused by a float being too high.
If you have stock needles, I'd put 150 mains in it, 40 pilots, set floats right and 3 turns and work your way from there.
That is a known good setup for that filter and pipe configuration.
Cool.
Buddha.