Author Topic: 1983 GS450tx Locked up engine  (Read 201 times)

Offline tavish

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1983 GS450tx Locked up engine
« on: March 02, 2020, 09:46:15 PM »
Good afternoon,

I'm having an issue with my 83 GS450, i know its not a gs500 however the internals are very similar. I rode the thing home running on one cylinder, put allot of time into it(rebuilt carburetors, upgraded lighting, mac 2-1 exhaust, its jetted correctly). I had it running great, suddenly it wouldn't rev over 5000 rpms, i pulled valve cover checked valve clearances and verified timing, put the valve cover back on, and cleaned my carbs again. It started and seemed to run ok, I let it get warm and it idled fine, when i twisted the throttle the engine rpm climbed to around 5500rpms and the engine shut down. now i cannot get the engine to turn over at all, pushing it in gear just skids the tire. the starter only clicks and gets the solenoid hot. I pulled the clutch cover off and removed the clutch as well as the crank to transmission gear, i can turn the transmission this way in all gears by moving the back tire so i know its nothing inside the transmission. I still cannot get the crank to rotate at all. one cylinder is all the way up and the other is all the way down.

Has anyone replaced a crank and rods in their gs twin? Is there anything else i can check by removing the stator cover? The bike only has 12k on the odometer. I would like to get this bike back on the road.

Thanks!

Offline cbrfxr67

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Re: 1983 GS450tx Locked up engine
« Reply #1 on: March 02, 2020, 10:00:34 PM »
I haven't but shazam that sucks. :cry:  I hope you can get it rolling again,...
"Its something you take apart in 2-3 days and takes 10 years to go back together."
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Offline tavish

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Re: 1983 GS450tx Locked up engine
« Reply #2 on: March 02, 2020, 10:03:10 PM »
Me too, I just purchased that exhaust and was really excited to get her going for the riding season. Not looking forward to having to split the cases on this engine. That and I have heard its a bear to remove from the frame.

Offline mr72

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Re: 1983 GS450tx Locked up engine
« Reply #3 on: March 02, 2020, 10:32:31 PM »
That really stinks. However, I'd say work your way down. Pull the cam cover and make sure the problem isn't a broken or slipped timing chain first, or bent valve that is stuck in the cylinder keeping the piston from moving up. You're going to have to do the top end anyway, so might as well start here. Then pull the head, see why it's seized, then you can pull the jug and inspect the rods. My bet is the problem is somewhere north of the rods. Plus once you get it torn down this far, the rest of the engine is a lot lighter to remove if you wind up having to tear it all down. With any luck the whole problem is in the top end anyway.

Offline tavish

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Re: 1983 GS450tx Locked up engine
« Reply #4 on: March 02, 2020, 11:39:01 PM »
Good thinking, i'll get cracking on that tomorrow. I heard these things were near bullet proof so i was shocked how quickly this one went south. I used to have a 95 gs500e and I beat on that thing daily with a 13 tooth front sprocket no less, it just took it in stride. If it is top end related I have read that I can swap the gs500 jug and piston assembly, plus with a spring upgrade and maybe a new pair of cams i can get around 60hp out of it. Either way, if i gotta do the bottom end, your right it will be allot lighter without all that other business on there.

Offline mr72

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Re: 1983 GS450tx Locked up engine
« Reply #5 on: March 03, 2020, 03:20:28 AM »
Well I'd say 60 hp may be a pipe dream. Gs500 gets max about 45. But anyway, good luck and let us know what happens.

Offline tavish

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Re: 1983 GS450tx Locked up engine
« Reply #6 on: March 11, 2020, 03:17:27 AM »
Sorry its been a while, i've been ill and haven't had time to wrench on her, I found the problem. Top end looks beautiful, bottom end is another story. I've got a rod froze to the crank, i'm thinking it spun a rod bearing. I have stopped the crank from turning and no amount of force is making this rod move whatsoever. So i'm shopping for a new crank. Does anyone have a line on getting new rod and main bearings for these old bikes?


Offline The Buddha

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Re: 1983 GS450tx Locked up engine
« Reply #7 on: March 11, 2020, 12:37:54 PM »
Sorry its been a while, i've been ill and haven't had time to wrench on her, I found the problem. Top end looks beautiful, bottom end is another story. I've got a rod froze to the crank, i'm thinking it spun a rod bearing. I have stopped the crank from turning and no amount of force is making this rod move whatsoever. So i'm shopping for a new crank. Does anyone have a line on getting new rod and main bearings for these old bikes?




There is a bunch of letters at the rear top of the crank case - behind the starter on top. ABBA types (no not swedish pop group)
Those are the letter codes of the bearings - atleast on GS500's they're there. The thinnest is A and thickest is C. If you can find it, that would be where I would start looking. BTW I think looking at a GS450 or a 500 motor is a better bet. In fact there is one 450 lying in the dirt at a junkyard in Gastonia NC.
If you want to get a look at a local junkyard for a 450, those aren't too rare, and the 500 motors are pretty common too.
Now I have a GR650 motor that fits in a 500 frame, may not fit the 450 frame cos its about 3/4" taller than the GS motor and your center rail will not allow that height. GS has the frame brace there which I cut and made unboltable.

Cool.
Buddha.
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Offline tavish

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Re: 1983 GS450tx Locked up engine
« Reply #8 on: March 24, 2020, 06:19:32 PM »
Ok have had not much luck finding a complete engine locally. Seen a few on ebay but the $600 price tags seem a bit steep. i purchased a crank and rods already assembled. any tips for splitting the cases? Also any preferred methods for cleaning out the oil passages other than hosing down with brake cleaner and blasting out with air?

Offline tavish

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Re: 1983 GS450tx Locked up engine
« Reply #9 on: March 24, 2020, 07:45:03 PM »
Well I have spoken too soon, someones got a complete engine 2 hours from me, i will be purchasing that. However i don't see this as a total loss as i now how a crap ton of parts for a bike that i intend to keep. Still think i should rebuild the engine i currently have while i cruise around on the replacement engine.

Offline tavish

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Re: 1983 GS450tx Locked up engine
« Reply #10 on: March 27, 2020, 02:03:43 AM »
Alright got my replacement engine in, got the old engine out. Took this pic in progress. Wasn't as bad as I thought to put the replacement engine in. I've certainly done worse with small block chevy motors lol. Hopefully be firing this up tomorrow. Going to finish wiring it, connect the exhaust, carbs etc. Also i think i'm going to swap my covers onto this engine as the ones that came with it don't look as nice. plan on saving the old motor for a rebuild. Excuse the mess i have allot of projects going on. Got seriously motivated today when the temps hit 75 degrees, saw allot of bikes out on my 4 hour round trip to get the replacement engine.