'82 750 kat with 1100 carbs

[Hippy161]

'82 Kat with 1100 carbs advice

 

Got an old 750 kat, bought unheard at good money. Stripped it before anything and cleaned it up. Sought advice on carb set up as its running 142.5 mains, pods and a straight throughish pipe. After months of work took it out today, carbs balanced and settings as best as I can. May I mention that rev counter doesn't work so can't give rpm. It runs flat in the midrange, which equates to say 60mph in top gear. Drop it down or give it a handful and slip the clutch and it goes great. As its 1100 (34s) on a 750 (which are apparently untunable 32s) can anyone give me any pointers if they have done this before. I've heard it was an accepted mod back in the day, just wondering if anyone has a tried and tested solution. Am running pods, 142.5 mains, standard (37.5 if memory serves) pilots and a fairly free breathing pipe. There are no air correctors which I would usually associate with pods of this era. Needles and tubes are standard as far as I know, needles are mid slot. Mix screws are at 3 turns. All the carbs were cleaned and blasted with air, diaphragms are good. All jets etc were sonic cleaned prior to running. 

Cheers, Dave.

 

Edited June 15, 2021 by Hippy161
Missed info, wrong topic title

[fab]

try lifting the need one slot.

[cnap504]

What are air correctors?  I have recently been on a mission to save old non running bikes.  I’ve done four sets of Mikuni bst cv 34 carbs, they all wound up using #45 pilots with good results 

[Sploofanoofa]

Ive had good results using 135 mikuni mains, good quality pod filters and standard needles on third clip. Good, free flowing 4-1 exhaust. This is all dependant on setup as all bikes will differ. What brand are your main jets? Ensure your ignition system is functioning correctly including timing. Nice fat blue spark etc.

Most brands of jets don't correspond with each other as with regards to exact sizes. There are good comparison jet charts online that cross reference mikuni, kehin and dynojet etc. 

Best bet is to get it as close as you can, then pop it on a dyno to be sure everythings happy. 

Have you carried out a plug chop in the range it gets a bit fluffy? Plug chop is a great indication for a rich or lean condition in a problematic area.

 

[Hippy161]

8 hours ago, cnap504 said:

What are air correctors?  I have recently been on a mission to save old non running bikes.  I’ve done four sets of Mikuni bst cv 34 carbs, they all wound up using #45 pilots with good results 

Air correctors just fit in one of the small intake holes and restrict air flow via a smaller than standard hole. They usually tap in via an m5 thread which you have to do. I've done it on my zed (750) running 34s. 37.5 pilots, 150 mains, air correctors, pods and basically a 4-fuck all exhaust. Runs great and torquey. Free through the range with absolutely no flat spots. I'm gonna try and make my own air correctors to see if I can tune these. 

[Hippy161]

1 hour ago, Sploofanoofa said:

Ive had good results using 135 mikuni mains, good quality pod filters and standard needles on third clip. Good, free flowing 4-1 exhaust. This is all dependant on setup as all bikes will differ. What brand are your main jets? Ensure your ignition system is functioning correctly including timing. Nice fat blue spark etc.

Most brands of jets don't correspond with each other as with regards to exact sizes. There are good comparison jet charts online that cross reference mikuni, kehin and dynojet etc. 

Best bet is to get it as close as you can, then pop it on a dyno to be sure everythings happy. 

Have you carried out a plug chop in the range it gets a bit fluffy? Plug chop is a great indication for a rich or lean condition in a problematic area.

 

Only run it for one day tbh but the flat spot is well apparent. Not got round to a plug chop yet. I've got 34s on another bike and might just emulate the set up to see if it works. Timing is bang on, freshly built motor and all in tolerences. Pipe is a cored Neta (which ordinarily were crap) which free flowing now, pods are generic K&N copies. Unfortunately rev counter isn't working so can't give the range where it clags up but reckon around 5k. It struggles to get past that but if you clutch it, give it a fistfull and slip the clutch two-stroke style it goes like hot snot. Once through the flat spot it goes well.

[Hippy161]

22 hours ago, fab said:

try lifting the need one slot.

Worth a shot. Costs nowt either.

[cnap504]

Yep, I remember now, the air correction jets to reduce air intake.  DynoJet used those a lot in their jetting kits.

[Sploofanoofa]

53 minutes ago, cnap504 said:

Yep, I remember now, the air correction jets to reduce air intake.  DynoJet used those a lot in their jetting kits.

ledar also do kits as well that restrict flow in the main air jet. Never been a fan of those however...

[Sploofanoofa]

56 minutes ago, Hippy161 said:

Worth a shot. Costs nowt either.

Worth a go. might need lifting/lowering/shimming etc. Easy enough. Sounds like your pretty close. Always time consuming ironing out the niggles. Hang in there, you'll get it sorted

[Hippy161]

11 hours ago, Sploofanoofa said:

Worth a go. might need lifting/lowering/shimming etc. Easy enough. Sounds like your pretty close. Always time consuming ironing out the niggles. Hang in there, you'll get it sorted

Its always a pain ironing the niggles, carbs off, carbs on, carbs off again (you know the script....). If I get a good set up I'll post for future reference so other can benefit