Gk73a sp engine troubles

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Tom123
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Gk73a sp engine troubles

Post by Tom123 » Wed Sep 04, 2019 1:29 pm

Hello all,

I’m in the process of rebuilding a gk73a sp engine.

Bought the bike as a non runner for £350 so st that price I expected issues!

However, on taking the bottom end apart I’ve noticed a tooth has snapped off of the gear on the crankshaft.

What are my options? Do other gsxr400 engines fit? Are the crankshafts interchangeable? I’m assuming my chances of finding a replacement crankshaft are 2nd to none.

mechannibalism
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Re: Gk73a sp engine troubles

Post by mechannibalism » Wed Sep 04, 2019 4:38 pm

If I'm not mistaken the Bandit engines will fit, but you have to cut off the mounting lumps on the cylinder head....has anybody done this?

moforockband
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Bike owned: GK73a SP CRM250 mk3
Re: Gk73a sp engine troubles

Post by moforockband » Wed Sep 04, 2019 4:53 pm

No, I've bought a crankshaft before from ebay for around £90 with rods. I wouldn't go bandit, as the cams are milder, and the part no for the cylinder head is different (which may mean it' has smaller ports or just a different colour ). The bandit head does not need any machining to fit.
Definitely keep as much as you can from the SP engine, they fly once they are in good fettle, they have lightweight valve train etc than normal gk73 engines.
You can use a crank from any gk73a model or bandit 400, but not the later gk76a as they have different primary gear teeth.
You can PM me if you want Tom, I used to race them, and rebuilt lots of these engines in the past.

Tom123
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Re: Gk73a sp engine troubles

Post by Tom123 » Thu Sep 05, 2019 11:18 am

Thanks for your help on this, no doubt I will be messaging you with questions when I’ve got all my bits together ready for the re build I’ll keep an eye out for a replacement crank for now though, I may try and speak to our welder at work and see if he can weld the tooth back on then get it fettled back to somewhere near what it was, probably impossible but he is somewhat of a magician!

moforockband
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Bike owned: GK73a SP CRM250 mk3
Re: Gk73a sp engine troubles

Post by moforockband » Thu Sep 05, 2019 8:43 pm

I wouldn't bother Tom, as it if ever came off, it may seize the engine, or do even more damage. There's a few on ebay now at decent money. You should re-shell your engine when you put it back together, but I'll leave that up to you.

Tom123
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Re: Gk73a sp engine troubles

Post by Tom123 » Fri Sep 06, 2019 5:32 pm

You make a very good point, I’m only trying to it corners but as you say it will bite me in the end. I think now it will just be a case of putting some money back and getting all the bits needed to re new the engine


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