GS450 cylinder head question....

[Fearlessmoto]

I have an 80 GS450, and the cylinder head needs replacing, i was wondering seeing that all the GS twins were pretty similar, and the engine hardly changed, could i use a newer GS500 head carb and exhaust combo on my old 450 block and cylinder? if not what mods could i make to get the most bang for my buck on a used head?

thanks everyone

[GregT]

Basically the answer's no...
The piston crown shape is very different 500 to 450 as well as the bores being different. What this means is that compression would be well down with the 500 head on a 450.
The positioning of the exhaust ports is a major pain also - they foul the 450 frame.
There have been recent threads here re fitting 500 top ends etc - with I remember a pic showing some very awkward exhausts.
I'd recommend a late 450 head with mild cleanup in the inlet ports.

Greg T

[Fearlessmoto]

thanks, i wasnt sure is there any cylinder head that would give me more compression? a 400 or 425 maybe? if not ill take your advice and go for the later model 450 head and clean up the ports. also can you swap bigger valves in the 450 head?

[BassCliff]

Greetings and Salutations!!

Hi Mr. Fearlessmoto,

I'm glad you've joined us. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", the Carb Rebuild Series, and the Stator Papers. Now let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

[exbellicus]

where are you located? I've got a spare 450 motor I could part out if needed

[GregT]

The standard 450 valve sizes are quite adequate - I'm running stock size in my race 450. Unless you change cams there's nothing wrong with the stock springs either.
If anything the stock inlet port sizes are slightly too large so just mild cleanup is all I'd recommend.

Greg T

[Fearlessmoto]

I live way upstate in New york, anyone familiar with plattsburgh? its kind of the rectum of the universe that no one south of syrecuse has usually ever heard of, and even though it's just a pile of brick by a river on lake champlain, it's my little pile of brick by a river