Gs40x crankcase with Gs450 cylinder & Head? does that work?

[Kris90]

Recently my Gs450 L seized the left conrod onto the crankshaft. its dead.

Now i have found on eBay an engine from a gs40x so a 400er i could buy tomorrow. in the pictures everything looks absolutely identical to mine, it even has no kickstart like mine. the engine only consists of the crankcase, Gearbox, flywheel... basically everything i need.

Now will my 450cc cylinder, Head, valves ect go straight on? because they are still all fine from my original engine and the new one doesn't come with any.

 

[Guest]

If you search back a few months you'll find my thread on doing exactly that.

Yes, it works fine; I have about 8,000 km on mine and no problems.

Given that you won't want to disassemble the whole block to change the rear cam chain tensioner shoe, you'll have to fabricate a spacer to go under your cam chain tensioner. This is because the cams sit a bit higher from the crank than on the X motor. I was worried that the different profile on the shoe would cause problems, but mine seems just fine.

It seems as though it is always the left con rod that seizes on these engines. I don't know why, other than it's further from the pump. The GS500 also. I suspect that it could be any number of things that would cause poor oil flow or pressure. So you may want to check out the oiling system on the 'new' block before you have the same problem. Oil pump o-rings? Pressure relief valve? Gaskets that seal the main oil gallery? Oil pan gasket? There are many places where an engine can leak pressure internally with no external way of knowing.

 

[Kris90]

Now i am not sure i understood that with the cam chain tensioner. see the tensioner bolts onto my cylinder, nothing there will change because I'm keeping my cylinder :/




Another question, i can also buy with the engine, the original pistons & cylinder.. but with no head & valves will my 450 head with cams & valves fit onto a 400 cylinder?

 

[Guest]

Now i am not sure i understood that with the cam chain tensioner. see the tensioner bolts onto my cylinder, nothing there will change because I'm keeping my cylinder :/




Another question, i can also buy with the engine, the original pistons & cylinder.. but with no head & valves will my 450 head with cams & valves fit onto a 400 cylinder?

The head was the weak spot on the GSX400. Parts for that top end are now scarce and some things unavailable. The 400 and 450 top ends are totally different. You must run all of one or all of the other.

The cam chain tensioner is the same, but must be installed with a spacer between 3 and 5mm thick or the cam chain will not be able to adjust properly. You will have to make the spacer as it's not a 'normal' part. I have a spare one which I could send you if you can't get one made there.

The reason for this is that the rear chain guide is a different part for the 450 and should theoretically be changed, but that would require complete disassembly of the block. The spacer allows you to run the 400 chain guide with a 450 top end.

 

[Kris90]

The head was the weak spot on the GSX400. Parts for that top end are now scarce and some things unavailable. The 400 and 450 top ends are totally different. You must run all of one or all of the other.

The cam chain tensioner is the same, but must be installed with a spacer between 3 and 5mm thick or the cam chain will not be able to adjust properly. You will have to make the spacer as it's not a 'normal' part. I have a spare one which I could send you if you can't get one made there.

The reason for this is that the rear chain guide is a different part for the 450 and should theoretically be changed, but that would require complete disassembly of the block. The spacer allows you to run the 400 chain guide with a 450 top end.

well thank you John! that makes a lot more sense. I am a welder & fabricator for a machine shop. would you be able to send me a picture of your spare, i will then get an idea of what i have to knock up