KZ650 turbo monster

about 2 months ago i aquired a KZ650 motor at a swap meet, Wanting to do a bike build i also went looking fro a frame, a buddy of mine gave me a 98 Cbr frame and KZ1000 swing arm with wheels and tires, in trade for some wiring work. then at my cousins scrap yard i found a nice little suprise, i found a TD04 turbo. i have been looking up KZ650 turbos just for fun. since i have all these parts for less than $100 id like to put a nice bike together for this upcoming season. This is my first time messing with a kawi and my first turbo build. any and all input will be super helpful.

The motor had been sitting outside for a year or two and when i pulled the head off i must say... wow, all four pistons were seized in the cylinders but 2 days and a bottle of marvel mystery oil later, and they were able to slide out with a little motivation. come monday i am going to have the machine shop at my tech school hone and deck the cylinders as they love to mess with motors and also want to mount the motor on the frame...
i need to know if the stock carbs can work with the turbo, if they are worth rebuilding, and i will need to get new pistons, what kind should i use? and any other advise yall would have would be great.
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also, i can get alot of work done for free with the shop at my school, so let me know of how to build this bike the right way.

WELL! I'd like to say I've been thinking about a KZ650 turbo for a while now, I've got most of the info in my head.

First question: How much boost? That will determine compression ratio required, whether you need an intercooler, etc.

Second question: Do you want to make the engine bigger? The only off the shelf turbo pistons are 810cc, for that you need a KZ750 block. If you're sticking with stock pistons, your boost will be quite limited due to a number of factors (see question 1).

Third question: You want to run carbs? Not easy with a turbo but do-able. Stock carbs will not work without modifications, if they will work at all. Others will be able to comment on this more than me. A fuel injection system from a ZX750 turbo would be the easiest way to get fuel into it.


Now that the questions are out of the way, let me run through a few things. First, if you plan to run the turbo in front of the engine, you will need a scavenge pump. Adding a turbo oil pan would be useful as well. As far as the engine goes it will be fine, the 650's are very tough. The easiest thing in my mind would be a fuel injection system and oil pan from a turbo 750, an aftermarket electric scavenge pump, your TD04 turbo (something smaller would be better though), and run about 8-10 psi of boost. That way you wont need an intercooler or anything fancy. A small oil cooler after the scavenge pump may be an idea as well.

So read that, answer the questions, and we'll go from there. A lot of it hinges on what YOU want from it. The sky's the limit really. I've been researching this for several years and I have most of the parts collected to do it RIGHT. But thats right in my mind, not necessarily yours.

The off the shelf turbo pistons have 69mm bore and a 16mm wrist pin. The 650 is 62mm and the 750 is 66mm.
You will have use a 750 block and sleeves. Fill out your profile and do a search. That is topic has been covered many times before.


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I'm pretty sure he can use a 650 block bored for 750 sleeves, but that's a little low on the list of things to worry about.

steell wrote: I'm pretty sure he can use a 650 block bored for 750 sleeves, but that's a little low on the list of things to worry about.

Understatement of the century haha. Its just "easier" to get a 750 block, since, where are you getting the sleeves int eh first place?

He can always go the way of the car guys. Small head spacer to drop down the compression of the stock engine, then you can fill your boots. Cometic would surely make someone such a thing if they asked. If using the stock pistons make damn well sure your mixture is rich, those cast pistons will melt in a hurry if its too lean.

The turbo is a mitsubishi TD04 49377-07720 it runs only 8- 12 psi boost and they run them on small 4cyl engines and bobcats

i was hoping to not have to make the motor any bigger, im a fan of 650s and id love to see what this monster can do. with that said i have looked and weisco makes pistons for the 650. am i mistaken or are these the turbo pistons? ive found multiple adds on ebay for them.

i would like to run carbs. FI is nice but tends to bring alot of problems with it, and alot of problems im not farmiliar with, im used to carbs, i would like to stick to them.

I do plan to run the turbo on the front of the engine, i looked and like you said i found a scavenge pump on MR.turbo. I may go with that

I would love for this bike to run at midnight maddness ( Friday night amateur drag racing) and go against some of my buddies.

Ok so given what you say,

Make a manifold
Scavenge the oil through a catch can back into the block with that pump (the catch can will cut down on foaming)
Get a small intercooler
Retard the ignition timing (heavier springs or less weight on the advancer)

To use the carbs, you need an electric fuel pump that will provide 3-5psi more than your boost level (so about 15psi). Then you need a boost referenced pressure regulator. Set idle pressure at around 3-5psi. You will need a fuel tank return line from your regulator. Then you need to run a line from the boost side piping (with a pitot tube is better) to the float bowls of your carbs, above the fuel level.

Note: This MAY work. I've taken what I know about blow through carbs and applied it here. I take no responsibility as I have no practical experience with this. You'd probably be better off with a big single like a Mikuni HSR for a harley. Less to worry about. You say that FI brings problems? It doesn't. A full setup from a 750 turbo would be plug and play here, as long as it was working when taken off the turbo. It would also mean you wouldn't need to do anything with the timing.

There are no 650 turbo psitons. There are Wiseco 810cc 750 turbo pistons. The Wiseco 650 pistons are 700cc, 10.25:1 compression, way too much for turbo.

I'm trying to help you, not trying to discourage. By all means, try it. You may blow up your engine but you may not.

I typed a whole lot of info, deleted it and gonna leave you this tid bit!!

:lol: :lol:

Les Holt

First thing I think he should do is go hang out on GPz750 turbo.
but to be honest I think he over his head and doesn't have a clue.

Blow through systems are a pile of shit. Good luck buddy........

There always has to be the first one to try something...

Stazi wrote: Blow through systems are a pile of shit. Good luck buddy........

This. FI is the only way to go. Carbs are not for turbos. But if he's adamant, then he can fill his boots.