XJ 650 Turbo to Non Turbo

Hi, me and a mate are building an offroader with a non turbo XJ650 motor in it. We bought the motor extremely cheap with almost no parts and found carbs and electronics etc for it. Since we got it going we noticed a bad misfire around 7-8000rpm and have checked everything for it. It also seems to have less than the standard 72hp the internet says it should have. Today I borrowed a compression tester and all four cyclinders are between 120-130psi, or around 8:1 compression ratio. As far as I can tell this is the compression ratio for a turbo engine? My question was is it possible to swap over the pistons from a non turbo into this engine to raise the compression ratio and cure the misfire/underpowered problem?

Thanks,
Grant

 

What's the vin number stamped on the engine, we can look it up and see what model of engine it really is!

 

You probably can go with the n/a pistons in the motor. Just make sure the heads are the same. If the head on the turbo motor has more volume in the combustion chamber, then you will need to swap heads along with the pistons. If they are the same heads, then you should be fine. But the camshaft will be different between the turbo and the n/a.

My thoughts are you may as well just get another engine. The turbo one will take alot of parts to make it n/a. Either that or slap on a turbo.

 

I finally got out to my mate's place where we keep our offroader yesterday. The engine model number is 17Y-000112 as far as I can tell from the internet, the 17Y was a 1982 XJ650LJ, a turbo engine. Also I wish it was as easy as slapping on a turbo, but it would mean replacing too much stuff for it to be worth it. Mostly because we designed our whole rear end for N/A horsepower, adding a turbo would need a new driveshaft, diff and halfshafts. I know a Yamaha dealer so ill see if he knows whether the heads are different or they are just low compression pistons they use in the turbo.

Thanks for your help,
Grant

 

The XJCD says the same as you found out on the serial number - starting with 17Y-000101 is a 1982 Turbo unit for your neck of the world!

 

Is there anyway to mount the turbo like it originally was? If you are using the stock driveshaft mounts then you should be able to put everything in place unless you did not account for the surge tank. The incoming line from the surge tank goes from the turbo underneath the engine to the surge tank.
As for the heads I am sure that they are different since the carb boots have different screw locations. On the turbo cyl 1 and 2 the screws are banked to the left, on cyl 3 and 4 they are banked to the right. On the Normaly aspirated 650's they are all banked to the same side. FYI, I am not talking about how the carbs are located but the two screw that bolt the manifolds to the head.

But to repeat what everyone else has said, using a turbo motor as a normally aspirated motor is extremely gutless. Expect to get passed by old to cylinder 400's

Sean

 

It definitly has a turbo head on it then as the carb boots bank like you stated. As for turboing it again, this is very hard mainly because of the cost, so far it has only cost us $1600 to build which is very cheap for what it is. By the way me and my mate are both 16 so we don't have money to throw at this thing. I would say there's room for a turbo to the left of the engine, but deffinitly not in the stock location. I think for now we will leave it how it is and well turbo it when we have the money to do a decent job.

Heres some old pics of our offroader in case you're interested...


XJ650 too powerful for my halfshafts


Offroader Video

 

That looks like a lot of fun. I'm now working as an Audio Engineer so I got to see and hear this at work, that is one very loud buggy. How deaf is the driver going to be?

 

I'm not sure how the turbo's on these work. I own a turbo car and can tell you that often times turbo engines are built with lower compression heads. If this can with a turbo engine, you will want to have that turbo on there to make it run properly. You'll never get the HP you should with out it. Sometimes it is as simple as putting the higher compression pistons in, and other times it is the heads too. Good luck! Nice ride!!!

 

It is VERY loud, but you always get out of it with a big grin Ive been looking around and found some small turbos from twin turbo 2L Subaru Legacys at my dads work, they have almost the same dimensions as the TC03-06A the XJ650 uses. Might look into using one of these in the future but for now I can't afford it.

Thanks for all your help,
Grant