83key hin carbs

so on my 83 kz 750 i have key hin carbs i just put a mac 4 into 1 on the bike and was told the jetting would need to be adjusted by one mechanic and told the jetting cannot be changed on key hin carbs can anybody help me with this issue

How is it running with the Mac ? Do you feel it needs to be rejetted ?

As long as you are not looking for tiny pilot jets you can get the necessary Keihin jets from Z1 Enterprises.
www.z1enterprises.com/SearchResult.aspx?...True&KeyWords=Keihin

They are only a dollar or 2 each so its cheap to try different sizes.

The stock jetting should be Secondary main = 125 and Primary main = 60 or maybe it's 62. With my eyesight I need a magnifying glass to see the numbers stamped on the jet :laugh:
If you have the stock airbox and are only rejetting for the 4->1 then try replacing the 125 with a 130 or 135. If that does'nt do the trick then go up another size. next try bumping up that 62 a bit.

Z1 dont list the smaller sizes but they do have them if you need them.

I'm thinking the 130 or 135 would probably do it.

All this is assuming they are Keihin CV34 carbs. I thought the 83 750 had BS 34s.

Good luck.

Oooops
double post

the bike seems to be running really rich (as in it smells like a gas station)i am working on a total rebuild of this bike its a slow process. i have noticed that my mileage has also gone down dramatically since i have installed the mac system (from 50 to 35 without baffles and 38 with baffles) i am not really sure which way i need to go. any help will be appreciated

If it smells like a gas station then I wonder if the carbs are leaking ??????


The only way to tell if it is running rich is to pull the spark plugs and look at the colour.
Black = rich
Tan = just right
White = lean

I think the NGK website will have some more exact detail and pics. Also. Do a search here on "plug chop".

the plugs are indeed black telling me that it is rich and there are no leaks but it still smells like there is a large amount of unburned gas coming through the system

If you have stock jets and you've gone to a 4 ->1 and have black plugs and smell gas then I think you have more happening than a need to rejet. It sounds like time for a carb rebuild.

Time to send carbs to wiredgeorge perhaps.

www.wgcarbs.com/

JR, While it is flattering to think that I could correct fouled plugs when the guy has stock jetting and an aftermarket pipe, it may not be possible. MOST fouled plugs are not the result of carb issues or improper jetting. We have tech articles on coil repowering and valve clearances specifically for this reason. It probably would help the guy's bike run properly for us to go through the carbs but I suspect if his plugs are fouling he should probably look to getting the ignition right and performing some basic tune-up steps.

i do have the aftermarket dyna coils on my bike and they are set up in the proper order to fire do i am not inclined to think that the ignition system itself is the actual problem. if you guys have any other ideas that would be great. ive been told by several long time riders that it is a jetting issue

cricketfire46 wrote:

i do have the aftermarket dyna coils on my bike and they are set up in the proper order to fire do i am not inclined to think that the ignition system itself is the actual problem. if you guys have any other ideas that would be great. ive been told by several long time riders that it is a jetting issue

if you guys have any other ideas that would be great.

Other ideas - - -


Good coils are of course important, but are only one ignition component, along with voltage being supplied, condition of plug wires, plug caps, and plugs. Where visual observation reveals a good fat spark at the plug tips, this is evidence that power and delivery of the ignition system are okay. Of course, timing of the good spark is also critical. If not already done, would remove plugs and actually look at the spark.

While there may indeed be a jetting issue, the reported symptoms are also consistent with other possibilities, such as too tight valve clearances. And the best way to eliminate that possibility, if not already done, is by performing a compression test on each cylinder and measuring all the valve clearances to assure the gaps are within specs.

Moreover, the reported symptoms are also consistent with possibility of a too high service fuel level inside the float bowls. If not already done, would check service floatbowl fuel levels, using the clear tube method.

And there's more, because the reported symptoms are also consistent with possibility of a leaking float needle/seat interface combined with an obstruction somewhere in the floatbowl overflow circuit (inside the floatbowl, or maybe a kinked or plugged drainage hose outside the carb). If not already done, would "sniff-test" the crankcase oil to help determine whether there's any fuel contamination.

Good precisely timed spark; adequate compression and proper valve clearances; correct fuel levels; non-leaking float needle sealing and properly functioning overflow circuits. All okay? Great!

After the above possible problem areas have been checked and eliminated, it would imo then be appropriate to address internal condition of the carbs (cleanliness of both fuel and air passages) and finally the jetting.

The peanut gallery has spoken.

Good Luck!

Well, since you already have loads of great advice from "long time riders", I will just wish you good luck.

so come to find out the people who seem to think they know everything from riding forever take their bikes to shops to get them worked on and dont do any of the work their selves. so i think i will have to try all the things listed and see if these are the problems. if all else fails i guess i could break down and go to the shop to have the bike looked at and spend the almighty dollar that i have tried to save so hard.