GT 550 Exploding starter motor.

[fineline]

Hello to all ! This is my first post here. I bought a 1973 GT550 recently and have been starting to restore it. It was a non runner with no key and I think hasn't run in decades. It's my first 2 stroke triple, and the strangest bike I've ever worked on. It seems to have some strange issues too. One of which is the starter motor which I removed today. I've never seen a starter motor this bad before. It looks like it exploded so violently it bent the bolts. I was so hoping for just a quick clean up of the terminals...
Are there any options available? As after some searching, I see they're a little hard to find.
Thanks in advance.

[barney01]

Hi and welcome to the forum. These bikes can be fickle but with help and experience most problems can be resolved.
With regards to your problem I have seen this before. The starter motor when activated spins the engine by engaging the starter clutch. The starter clutch has a series of feet on the bearing that grip the spinning starter motor. When the engine fires the momentum of the starter clutch then releases the starter motor. If the feet don't retract the engine speed destroys the motor.
So I think it's a starter clutch bearing problem.
Some more info for you. There are 2 makes of starter motor Kokusan and Nippon Denso. It's worth noting that the GT750 has the same motor but different end cap which can be changed
It's worth mentioning that there are 2 types of starter clutches which are drastically different and the early ones are famous for falling apart!
BAZ on here has a contact to repair motors.
Here is a topic which may help you
viewtopic.php?f=16&t=7137&hilit=Starter+motor
Good luck

[fineline]

Thanks Barney !. I'll have a look at the starter clutch, I'd hate to just fit another motor, only to blow that one up too.
The GT750 info is good to know too. Just hoping I'm not going to discover too many horrors on this bike, but that's the gamble I guess.

I'll check those links out too. Thank you!

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Is there a way of checking the starter clutch operation without a starter motor? I have the side case off at the moment to check things. Plus the clutch plates are seized anyway.
Thanks.

[barney01]

The short answer is no.If you have the cover off, I would suggest it would be good practice to get the clutch plates off. They will need to be cleaned and the metal plates can be lightly sanded with fine wet or dry paper to remove any debris. The clutch basket is held by a single large bolt. You need to inspect the fingers of the basket for ridges as that can affect clutch operation. The starter clutch on the back of the basket can then be inspected. If it's the early starter clutch they are known to crack and even fall apart. The later Borg Warner is much more robust.

[fineline]

Thanks for that! I removed the clutch plates but just couldn't get the clutch nut off without one of those special holding tools. Sadly I've mashed the nut up a bit while trying various ways of doing it. So another part to go searching for. . I'm really not having much luck with this bike.

[barney01]

Great investment! Used mine many times
https://www.ebay.co.uk/itm/125558788702 ... media=COPY

[fineline]

Thanks, I ordered one of those tools just after I ruined the clutch nut and found they're a hard to find item too. It was made of very soft material.

[barney01]

https://www.classicsuzukiparts.nl/winke ... 9140-22003
I've used this company in Holland many times very quick delivery

[fineline]

Thanks again Barney your a life saver! Ouch on the postage cost but that'll teach me to be so brutal...possibly.