rs 34mm wont idle

Kz 1135cc,12.5cr pistons , stock valve size , has been mildly ported. Bigger cams .395 lift . I have rs34mm carbs on it . 125 main jets , 17.5 pilot jets stock needles and stock needle position . Bike will start and idle at 2000 rpm . But when I turn the idle screw down to bring the idle down it stalls. Even if I turn it a hair it stalls . So I tryed 22 pilot jets and now it will idle down to 1000 rpm for a minute and stalls . If I whack the throttle open to 3k to 4k it won't drop to 1000rpm but back to 2000 . Some times it will Rev up to 2000 and drop to 1000 and back up to 2000 without even touching the throttle . I checked for slide sticking in one of the carbs and they are all synchronized also checked for intake leak and head gasket leak. Wondering if I should try a bigger pilot jet? Or if it could be something like the dyna s ignition pickup . All cylinders are firing just a few degree difference across all four .and I am running 110 octane gas . Any ideas ?

sounds lean. how many turns are the idle mixture screws out?

At the moment there at 1/4 turn out from bottomed out . I tryed turnin them out about 2 turns and nothing am only getting a very Lil different sound of the rpms raising at 1/4 out . Tomorrow I'll try again turning them out 3 turns this time . I did just read u can go up to 3 1/2 turns with out having to change jets . Do u know if timing or a valve not closing all the way could cause something like this ?

I have no answer for what is going on with your bike. The carbs sound ok. I would have questioned the carb sync, but you have done that. Bikes ignition timing comes to mind, a faulty ignition as a possible issue. You problem is most likely other than the carbs.

What do the plugs look like, most likely are black as night. Way to rich. Do you smell a un-burnt gas fume?

I have RS34 on my bike. I also have a AFR tuner.

I have been in the process of tuning my bike. Even with the AFR its not easy.

You want to fully use the accelerator pump. I have the pump fully adjusted.

Here is my current tune:

P-6 NEEDLE JET ( up two sizes from stock P-4 )
-3 ON JET NEEDLE ( stock position )
125 MAIN JET
17.5 PILOT JET
0.8 AIR
1 TURN ON AIR / FUEL SCREW ( you don't want to go more than 1 1/2 turns. ) this gives me 12.8 AFR at idle.

You don't need 22 pilots. If you went 20 pilot, I would turn screw out 1/8 turn.

The air fuel screw has an operating range. The range is 1 to 1 - 1/2 turns max. If you need to open a 17.5 up more than 1-1/2 then move to a 20 pilot.

This tune has me very close to optimal setup.

OK today I turn the air screws all the in and 3 1/2 turns out. No change in idle speed and I still can't not get it to idle below 2000 rpm . Rechecked base gasket, head , intake and carb gas gaskets with starting fluid no air leaks . Also thought it could have been the turbo blue in the gas tank I emptyed tank and refilled with 93 octane no change . Readjusted throttle cables and nothing. Putted the plugs and looked into jugs #1 and #3 pistons looked very clean could still see metal on the Pistons but they did look kind wet with oil . But there is no smoke coming out of the exhaust . #2 and #4 cylinders pistons had some carbon build up couldn't see metal on pistons . . When I took off the gas tank I did see a lead on the coil for #1 and #3 only had a few copper wires in the eyelet so I restriped wire and put on a new connection. Maybe it was intermittently firing cause they pipes were all hot . I haven't try starting it yet have to wait till tomorrow cause it got later out and just way to loud to start I will let u know what happens with that . If still doing the same thing am going to take carbs off and reclean them and drop the pilot jets back down to 17.5 . Any input or ideas will definitely help and appreciated thanks spark plugs in order left is #1 right is #4

OK so i reconnected the coil wire and replaced the spark plugs and still the same thing still not idling under 2000 grand also more the timing plate retarded it all the way and advanced it all the way still made no difference. So not I will take the carbs apart and clean them and check sync and float height and possibly replace needles and air jet screws . Any suggestions on the needle size or should I replace some of the stock size?

Who did the porting of the head.

The porting of a KZ head needs to follow some important rules. If the person doing the port work thinks bigger is better, just hack out the passage and enlarge it ......... will cause many problems.

How many times have you done a carb sync?

do you really know what you are doing?

what rpm did you set bike at to do the sync?

A bad carb sync will kill a bikes proper idle faster than a 357 magnum to the temple.

Yes the heads are ported . I do not know who did the heads . .. I purchased a complete motor from a guy . It's a 1105cc theses heads and 34mm carbs on it put it in my frame for a few months and it ran great . I then came across a new complete 1135cc for $500 the guy had it professionally built 12.5 cr pistons and the head porting is even bigger with bigger cams .480 lift and bigger valves 38/32mm I belive. I was told that he put around $3000 into the heads alone . the guy never even started it . So I put it in my frame and with the 34mm carbs off the 1105cc motor and it ran fine till a week later one of the vavles droped into the cylinders damaging the head lucky the piston was not damaged that bad just a Lil tiny tiny knick on top of it . So I decide to put the head off the 1105cc motor on the bottom end of the 1135cc motor and this is the result. Which I do not get at all because I have ran these carbs and they worked wonderfully and this is before I started making changes to the jet sizes . And as far as the carb sync I checked them when they were off just by seeing if they were all at the same height at rest made sure they are lift at the same time and that they were at the same height at half open and full open . But as far as snyc them on the bike i have never done that i know i should use a vacuum gage when it's running but there is no ports on these intakes because they do not make them for the bigger carb intakes . I was thinking about making my own by drilling a hole in the side of it and inserting a tube and jb welding or epoxy them in .

That's also why I was wondering if timing would cause the motor not to idle .cause I had to take the timing chain off . I reinstall it by the book matching the arrows up that are on the sprocket with the top egde of the head . And counted from the 1st pin of the chain after the exhaust arrow so that the 28th pin would be on the 28th marker on the intake sprocket . But I know these cams have been degreed 110 . So would that change were the arrows on the sprockets should be sitting with the top edge of the head? When it's at 2000 rpm it sounds good no missing and when I Rev it up it sounds great no coughing no hesitation throttle response is very crisp and drops right back down to 2k fast .

the carb sync ports are on the carb rack? if you don't know what you are doing.......get someone to help before you break it.

Are you using .480 lift cams on a 1105?

I have .395 lift web cams at 110 on both, no that's not the problem.

Didn't know you could run 38/32 valves on a pre-J head, would have valve contact due to overlap?

You are way out of your league right now. You need to slow down, study and gain some insight........maybe stop and get a plan to move forward.



If you look on the carb rack, the rubber nipples on the engine side of RS34 rack are for carb sync vacuum gauge. Why did you claim to have done a carb sync when you didn't.

No am not using the .480 cams am use the smaller ones that are .385 I think and i said i did a bench sync not a vacuum sync . The other day I started it again it was smoking really bad out of the exhaust think and oil was leaking out of the head gasket so I think am going to sent the head in and have it rebuild and milled and try again

Give this guy a chance at the head. He is one of the best.

www.cavanaughracing.com/