GSX400 engine in GS450?

[Guest]

Hello!
My poor old GS450 stands abandoned in a shed since the british bikes steal too much time. Engine is working but quite worn and should do best with at least a head job. Now I got offered a well working GSX400 engine for 80 pounds which feels like nothing. Does it fit without frame alterations?

Best regards
/Viktor Boström, Umeå Sweden

[John Park]

It's a direct bolt in. The parts you'll need such as plug connectors [smaller] are easily sourced. The lower engine is identical, but everything from the cylinders up is different, but that doesn't matter.

The carbs are slightly different in jetting, so if you can get the carbs with the engine it would be nice. It may run a bit rich with 450 carbs on it, but it's just a matter of adjusting the needles a bit.

You'll get less torque below 6,000 but above that they're pretty even.

[gofika]

It's a direct bolt in. The parts you'll need such as plug connectors [smaller] are easily sourced. The lower engine is identical, but everything from the cylinders up is different, but that doesn't matter.

The carbs are slightly different in jetting, so if you can get the carbs with the engine it would be nice. It may run a bit rich with 450 carbs on it, but it's just a matter of adjusting the needles a bit.

You'll get less torque below 6,000 but above that they're pretty even.

Thanks for the answer!

The bike is totally destroyed in a puritan's view. Has a home made manifold and an SU from a 60's Mini which I think I intend on keeping if I do the swap

The GSX being an 8 valve has no real advantage? As said before the money is not an issue, but I had a hunch it would have a bit extra on high rpms but no?

Cheers!

[John Park]

The only advantage I can think of is the screw adjust valves. Personally, I'd just as soon have shims, but it does mean you don't have to go looking for a different shim while your bike is apart.

There's no power advantage. There could have been, but then you'd be revving to 12,000 and generating more heat than the head could get rid of; it's a bit challenged for finning as it is. The heads have a reputation for cracking around the exhaust valve seats and up the spark plug hole. Later heads were supposed to be better ['83 on?] but it depends a lot on how hard it's been run.

I've seen the cams and rockers gone, which is usually a result of running with tight valves which grinds a divot into the rocker. On the bright side, the motors are pretty efficient and pretty good for cylinder, ring, piston wear and cooling.

I took a dead one and converted it to a 450; my original GSX400 motor is getting converted this winter. GSX400 parts are scarce in Canada and non existent in the US, so 450 is the way to go. Plus it gets hot here and the 450 cools better and is more tolerant of crappy gas, being lower compression. Many GS500 bits will fit, also.

Don't get me wrong; I enjoyed the 400, but the 450 is a more practical choice over here.

[gofika]

The only advantage I can think of is the screw adjust valves. Personally, I'd just as soon have shims, but it does mean you don't have to go looking for a different shim while your bike is apart.

There's no power advantage. There could have been, but then you'd be revving to 12,000 and generating more heat than the head could get rid of; it's a bit challenged for finning as it is. The heads have a reputation for cracking around the exhaust valve seats and up the spark plug hole. Later heads were supposed to be better ['83 on?] but it depends a lot on how hard it's been run.

I've seen the cams and rockers gone, which is usually a result of running with tight valves which grinds a divot into the rocker. On the bright side, the motors are pretty efficient and pretty good for cylinder, ring, piston wear and cooling.

I took a dead one and converted it to a 450; my original GSX400 motor is getting converted this winter. GSX400 parts are scarce in Canada and non existent in the US, so 450 is the way to go. Plus it gets hot here and the 450 cools better and is more tolerant of crappy gas, being lower compression. Many GS500 bits will fit, also.

Don't get me wrong; I enjoyed the 400, but the 450 is a more practical choice over here.

Thanks for a genuine answer!

I go a little by the philosophy "the one that has most old junk when he/she dies wins" and 80 pounds are very little money even for a single parent doing social work for the government, so probably I'll get the engine. We'll see.

Converting GSX400 to 450 = what needs to be done? Just change of cylinder and pistons or more complicated? Interesting. Or did you actually mean converting a GSX400 to a GS450 - not GSX450?

Cheers!
/Viktor

[John Park]

Thanks for a genuine answer!

I go a little by the philosophy "the one that has most old junk when he/she dies wins" and 80 pounds are very little money even for a single parent doing social work for the government, so probably I'll get the engine. We'll see.

Converting GSX400 to 450 = what needs to be done? Just change of cylinder and pistons or more complicated? Interesting. Or did you actually mean converting a GSX400 to a GS450 - not GSX450?

Cheers!
/Viktor

The X refers to four valve head motors. There's a thread not that far back - mine - on converting GSX400s to GS450s. It's just a bolt on. The only possible snag is the rear cam chain guide, which is slightly different and would require splitting the cases to change. I had to make a 3mm spacer to go between the tensioner and the cylinder block to make up the difference: it would work, but the tensioner was pretty much bottomed. I've put about 10,000 Ks on the motor and all is well. The front guide should be a 450 one [slightly longer] as well, but I've been running a 400 one with no problems, but I'll change it when I check the valves next.

For 80 pounds you'd probably get that much in various spare parts anyway.

[gofika]

Yup I know that, I guess an eight valve 450 would be nice, but the heads and pistons/cylinders don't match up I take it?

You mean 80 pounds is not cheap for a running motor? I'm not a native english speaker so some stuff misses me

Cheers

[John Park]

An 8 valve 450 would be possible; I think Greg T in New Zealand built one up to race, but it will be expensive +. Putting GS500 cylinders and carbs on a 450 is the usual way to go for more power at low cost.

What I meant was that even if the 80 pound motor doesn't work out, you'd get that much in spare parts out of it, over time. You can't really lose.

[gofika]

Sounds nice! Still haven't decided, the engine is 700 km away so we'll see what happens