Help a newbeginner..

Hi,

I have purchased a Kawa 81 modell orginal 650CC, but the previus owner have replaced the engine With a 750CC, but he has not replaced the carburettors, please see Attached Pictures. I have talked With a local workshop and they was sceptical, because the 750CC orginal has not mechincal carburettors but vacum carburettors... ???

The reason I started to looking into these is that the bike is noting going Perfect, only on idle...
I started to clean the carburettors and wanted to order some new parts and then my local workshop told me that these was 650CC carburettors....

Must I by new carburettors or new engine ???

Thank you verry much Your help and inputs !

The engine doesn't really care which style of carburetor is used, the problem will be the carburetor holders and the air box to carburetor hoses. It will be simpler to sell the carbs you have and purchase the correct ones.
Is the air filter box installed and properly hooked up? Did the carbs fit snugly and seal properly to the carb holders?

Did you try installing the carburetors on the 750 engine yet?
Do you have the 81 650 carb holders & airbox ducts? and is the rubber soft?
In the USA the 81-83 KZ650 came stock with a 750-4 airbox.
Check to see if your airbox is embossed or labeled with KZ750 E/H or something like that.
The 750 markings are on the top/left/front of the airbox above the duct holes.

If your carb holders & airbox ducts are good, then you can use the VM24 carbs.
They will need to be rejetted & tuned. The 750-4 engine is approx. 13% bigger.

Hi all.

Thank you for the feedback, the carburetors was installed to the engine, please see Attached Picture.
The person I bought the bike from has bought it from another owner so the peson I talked With has not driven the bike...
So I don`t know if the bike has been used With these setup, but I assume it has been driven... but don`t know, havent been Abel to come in contact With the other owner...

As you can see from the Picture it has been installed New air filterrs "short" one and not air Box...?

So the only problem for me is to avoid any vackum leaks between the carburetors and the inlet on the Block, and change jets?
If I figure out what jets I have will you be able to understand if they are correct one for me? Maybe the previus owner already have done it?

The seller told me that if it was long time I was using the bike I had to have the fuel switch in pre for a will,
before I set to ON, he dident know why and found it strange...

When I start up the bike it start without any big problem with choke and it goes fine on idle.
When I try to give throotle the RPM goes some higher but are suffocate it self, but if I relase the throttle it goes back to running
fin on idle. I also obersvered that when it suffocate it sometimes "poops" and it comes petrol gas out from the air filter on
one of the filter. It also comes "poop" sounds...

I tried to switch of the bike and let switch the fuel switch to PRE again and when I startet up next time it was tottaly different
when I tried to giving throttle, the motor respons on RPM on my throttle no suffocate observation. I started to drive
and it working some minutes fin on 1 and 2 gear, but then it start giving problem again... I tried to give full speed on the throotle
and then wroooom the engine was giving me heavy accelartion.

After these experience I have dismounted the carburetors for cleaning, and I contacted my local workshop for some seals to the carburetors
and then workshop told me that these carburetors was for 650CC and not 750CC... and I posted these tread on these forum for help..

I hope you all undersand my English...

Thank you verry much for using time to help a new beginner...

Previous owners often provide false information. I suggest you first verify that the engine is a KZ750 engine; it may be a KZ650 engine. To verify, look at the area of your engine as shown in the image below to see how it is marked.

Regardless of which engine the bike has you will be faced with a challenge to properly tune it because it has those pod air filters instead of the air box. If you can find an airbox you can install the stock jets in the carbs and clean the carbs and they should work fine. Otherwise you may spend a good amount of time, effort, and money finding an acceptable jetting combination. Ed

I'd check the valve adjustments before going any further.
Steve

The CV vacuum carbs and the older 'slide' carbs have a different cylinder head, hence the change of carbs with the later motor.

Your fuel leak out of the airbox is a stickly float or worn float valve, fix that first. While you are there check your rubber diaphragms on all the slides and note the sizes of any jets and the needle.

Read up on the ' clear tube' float height setting method.

Also careful setting up carbs on the road - as a beginner you may be shocked just how powerful that bike is.

1981 650 w VM24 carburetors.


In general with pod filters & aftermarket exhaust increase the main jets by 1-2 sizes per airbox or exhaust change, increase the pilot jets 1 or 2 sizes, & re-clip to raise the jet needles. So for a USA KZ650 w pod filters & aftermarket 4-1 exhaust use #110-115 main jets (estimate). #17.5 pilot jets, & re-clip the jet needles.

750-4 engine. Additional adjustments are needed for the 750 engine. I guess increase the main jets 2 or more sizes beyond what's appropriate for the 650 w pod filters & 4-1 exhaust. ??? I'm not sure if the pilot jets would need to be increased more or not. maybe go with #17.5 or #20 pilot jets. ??? Not sure if the jet needles should be clipped higher at the 3rd groove. ???

I guess increase the main jets 2 or more sizes beyond what's appropriate for the 650 w pod filters & 4-1 exhaust. ???

This is just where I would start for any 4 stroke bike, but conversely the GPz750 with a 4-1 and pods needs a big step up, on the main jet to somewhere around 140 IIRC , Very close to the 1100 jetting, Strange but true.

If the engine ran better with the fuel valve on PRI, then the valve may not be working properly. If it is a vacuum operated valve, there should be a vacuum hose from the valve to a similar port on one of the carburetors. If that hose is missing or cracked, the valve will not operate properly. Also, the rubber diaphragm inside the valve may be torn or sticking.

If that hose is missing or cracked, the valve will not operate properly.

...even worse could make one pot run lean and cause overheating as well as chronic carb inbalance..

Thank you all for putting effort into helping me out!

I have now been able to talk with the previous owner and he says he have used the bike alot the last 5-6 seasons without any big problems, same engine and carbs as is installed now... question if I can trust these if yes, then we are talking about carbs cleaning or air leaks between the carbs and block inlet...?

I'm away on hollydays so haven't been able check thing physical, but quite sure it stand 7xxx on the block not 750, but something around was it maybe 747 ???

When I'm back will I write down the jets says and provide it here.

I think there was a problem with the level regulation in the resorvar because I observed it was coming out gass from the drain screw randomly on each carb...,

I have dismounted the carbs completly now and used carb cleaner and high presdure air on all parts. But I was stupid not record the position on the idle mixer screw....

Shall it be a spring on the mixer screw? There was a spring on one of the carbs only... the spring avoid the screw to move by vibrations?

Plan further:
1. Check compression on each cylinder.
2. Write down jet says and give you all the information.
3. Put the carbs together.
4. Screw the idle mix screw full inn and 2-2,5 turn out and try to start up?
5. Take a quick carb sync?
6. Play with the mixer screw to fin the point where the cylinder dies and turn the screw 0,5 in. Do these one by one on all 4!
7. Maybe finish? Hehe