GS450 Surreptitious Engine Reassembly

[free99]

Hey Guys (and Gals?),
Hope everyone's having a great week.

I lost all my oil a month or so back and managed to seize the engine. In spite of advice saying to "just buy a new engine" and other expensive options, I've decided to try my hand at repairing my old gal, if nothing else than to learn more about these engines, and engines in general.

I've never taken an engine apart, so I'm a wee bit out of my comfort zone. A couple of pointers and advice would help a lot in getting me back out of the forest.

Questions:

1. How do I ensure that the counter-balance is correctly oriented when I reassemble the crank assembly into the case?
2. Is there anything I should pay attention to that isn't so obvious now that I have the case split?
3. Do I need to add any RTV to the case halves when reassembling, as it looks like there was a little bit already in place
4. Is it a bad idea to blue loctite every bolt as I reassemble?

Some remarks: Those two hex nuts up above where the oil filter goes are literally the toughest bolts I've ever had to crack in my life. Also, don't, don't, don't buy a polymer movers dolly from Horror freight to rest your engine on, 1000lb capacity be damned. The surreptitious part of the title is because I'm doing this engine work against my complex's rules right in my carport.

Pics next post.

 

[free99]

Step 1: Take everything off


Slight bit of scuffing on one of the camshafts. Is this ok? The texture is barely perceptible after cleaning with brakleen and my clean ungloved fingers.
I saw someone mention using metal polish, a rag and a twice-looped shoelace to sort of buff the surface.


1000lb capacity my fat ass.


Wow. Beautiful. Once pressure was relieved, things seemed to slide ok. No obvious scraping or marks on any of the plain bearing surfaces. How do I make sure everything is correctly oriented once I reassemble?


This is on the maximal thrust-recieving side of the plain bearings. Babbit seems gone, but the metal of both crank and this insert are both smooth. I ordered replacements, though I understand I may need different color codes once I check with plastigage.


Hard to capture while stealthily doing this at night, but no nicks or gouges. But that may be a lack of experience on my part. How do I know what's "serious"? (Actually asking).

 

[Nessism]

Do you have a copy of the factory manual?

 

[Rich82GS750TZ]

This guy?s whole YouTube series on a GS 550 rebuild (4 cylinder, not a twin) is excellent and enjoyable to watch. He was very thorough in his documentation of every step. I watched them all. Will give you a good idea what you?re up against. I personally am not into caf? racers, but think his bike is very tastefully done.

Urban Monk TV

 

[fbody_mike]

Good on you for diving into the engine tear down. Like Ed said, the manual is out there, do you have it?
The bottom end, from what what I can tell so far doesn't look like a motor that had locked up. If you do not have these things yet, I would get them soon, even the Harbor Freight stuff is ok, a torque wrench, some Vernier Calipers and some metric taps to chase some threads.
As for what to add thread locker to, see Ed's mention above, the manual will state what bolts and nuts to add thread locker.
How do the cylinders look? All motors I have seized needed oversized pistons and a rebore.

 

[free99]

Many thanks for your advice so far fellas.

Ed, I have the engine portion of the factory service manual as well as torque specs printed out.

fbody_mike, I've got both a digital vernier and a digital micrometer, metric taps, a digital torque wrench and a moderately young back to handle all this hunching over a carefully shaped assembly of metal.

HAven't looked at the cylinders yet, I oiled them with Marvel Mystery via the spark plugs first thing once I was towed home. They slide as I struggle to remove the con-rod caps (is that the correct term?) but I expect at the least a honing is in order, I rented a compression-check kit too. I'll handle the jugs/upper portion later, if that's sensible to you folks.

Rich, thanks for those videos, I'll be watching the rest of the dude's videos tomorrow.

It's a lot of work, but it's nice to learn something new. I expect a few years from now I'll be wondering why I thought hunching over an engine was a good idea, but it sure beats drinking myself to sleep :drunk:

I found the point about the counter-balancer, specifically matching the punch marks. I really admire the Japanese for their attention to detail beyond factory floor assembly. And their foresight to listen to W. Edwards Deming, for helping to foster their culture of quality which the US industries ignored, and are still playing catch-up on.

 

[Guest]

This is all very doable without experience, my first foray into the Suzuki mechanical world beyond just oil and filter changes is exactly what you're doing now, although my engine rebuild was triggered by my own mis-diagnose of a gearbox issue rather than having it seize up.

Sounds like you've got all the right advice to start with (and I'm no guru either) but will keep an eye out in case I can add anything useful.

Good on you for tackling this also!

I'll potentially be revisiting the top end of my own 450 some time next year as the compression is down a bit. When I rebuilt it, it had something like 96K kms on it, and it was so clean inside I simply installed new rings, cleaned everything up, and put it back together. I've since done around 90K kms on it so I have no doubt it's time to consider a big bore kit and possibly some valve seat TLC to get it humming along nicely again.

 

[free99]

Hey Pete, appreciate the kudos.

So a quick question: What is that part with the little nub & spring? I'm not sure where it came from in spite of my best efforts to stay organized.




Took the big ends off the connecting rods. Ooooof. The babbit from the inserts actually dug its way into the oil holes on the crank.



Luckily I was able to push it out in mostly contiguous pieces with the flat end of a 2.5mm hex driver


Crank's looking pretty bad, man. Forgot to take a pic once I'd cleared the oil holes.


WD-40 Oiled 250 grit and light but fast sanding with a doubled shoelace..


Then dry 1000 grit, followed by WD-40'd 1000...


Last pass with a piece of cloth and Noxon metal polish (I think they got the idea for the name from how noxious it smells), then a dry cloth. Do the polishing again, if the finish isn't quite up to par.

After cleaning all oil holes with carb cleaner from top to bottom, then air blasting and careful inspection, the surface looks almost mirrored and there is no obvious debris in the oil holes.

The finish wound up better than the pic shows. Added some oil from the top oil hole to prevent any flash rust, inside & out. I'll keep you all posted.

 

[Guest]

The crankpin diameter is 34mm. The clearance is .001" - .002". The good news is that it appears the babbit got hot and smeared on the crankpin before the crank journal had time to get hot. Typical rod bearing failures are 'end of crank' damage. You'll need to very accurately measure the journals. The crankpin pretty much has to measure within a thou of that 34mm.

The crank is a centrifuge, spinning oil off at a huge G load. If it's leaving faster than the feed can supply, the bearing fails. There isn't any room for error at 9,000 rpm. If you can get within the .002 limit for clearance you should be fine. More than that and you're better off searching for a crank.

 

[free99]

I understand what you're saying John. I don't really have a way to measure ovality of the part, just a harbor frieght digital caliper. I'll do my best with an non-professional tool. I wonder if there's any part within the engine I can use as an accurate measurement to compare what the calipers read?

I'm taking a leap by ordering crank pin inserts at the -020 thickness, so I can at least do the plastigage measurements. If the measurements go beyond what the thickest inserts Suzuki sells can handle, new crank time for sure.

A question: I was under the impression that people remachine their crank surfaces on occasion when things like this happen, and in fact that'd be why Suzuki sells inserts of varying thicknesses, besides accounting for their internal machining variances. Isn't that true, or am I drawing strange conclusions?

 

[Guest]

Hey Pete, appreciate the kudos.

So a quick question: What is that part with the little nub & spring? I'm not sure where it came from in spite of my best efforts to stay organized.

Your crank questions are a little out of my league unfortunately, the only crank issue I've had to deal with was the Katana crank needing truing up which I got a professional to do for me.

However, I can answer your spring question, and that's the bit that indicates the gear position in combination with the gear indicator switch. The gearbox shifting shaft has a hole in the end that sits under the sprocket cover and those get inserted in there, and the gear position indicator switch mounts over it. You'll see some contact pads on the underside of the gear position indicator switch, and that little nib rotates with the shifting shaft to ground those contact pads when in each gear or in neutral.

Here's the parts fiche link from the dealer I use here, you're looking at parts 41 and 42: http://www.mickhone.com.au/partFinder/fiche/suzuki/1980/gs450/gear-shifting#content

 

[Rich82GS750TZ]

This just so happened to be my entry in the pic of the week game this week.

 

[Guest]

I understand what you're saying John. I don't really have a way to measure ovality of the part, just a harbor frieght digital caliper. I'll do my best with an non-professional tool. I wonder if there's any part within the engine I can use as an accurate measurement to compare what the calipers read?

I'm taking a leap by ordering crank pin inserts at the -020 thickness, so I can at least do the plastigage measurements. If the measurements go beyond what the thickest inserts Suzuki sells can handle, new crank time for sure.

A question: I was under the impression that people remachine their crank surfaces on occasion when things like this happen, and in fact that'd be why Suzuki sells inserts of varying thicknesses, besides accounting for their internal machining variances. Isn't that true, or am I drawing strange conclusions?

There are four, colour coded , sizes of standard bearing shells. They cover a range of about a thou. There are two undersizes for crank regrinds at 1.625mm and 1.750mm which correspond to .010" and .020" under regrind.

As you can see, the tolerances are pretty precise. I'd take the crank to a machine shop and have them measure the journals you have. If the number comes up at 1.3376" [33.976mm] or larger you can use the crank. If less, you're probably best off looking for a used crank. I'm not sure if a GS500 crank is the same. ??

I'm not sure what you mean by crank pin inserts. Connecting rod bearings of .020 undersize are thicker and will not go over the standard crank; you'd need the standard bearings to do it that way.

 

[free99]

There are four, colour coded , sizes of standard bearing shells. They cover a range of about a thou. There are two undersizes for crank regrinds at 1.625mm and 1.750mm which correspond to .010" and .020" under regrind.

As you can see, the tolerances are pretty precise. I'd take the crank to a machine shop and have them measure the journals you have. If the number comes up at 1.3376" [33.976mm] or larger you can use the crank. If less, you're probably best off looking for a used crank. I'm not sure if a GS500 crank is the same. ??

I'm not sure what you mean by crank pin inserts. Connecting rod bearings of .020 undersize are thicker and will not go over the standard crank; you'd need the standard bearings to do it that way.

Ah ok, replace "pin insert" with "bearing shell". That said, I'm certain I've reduced the diameter of the crank's journals for the connecting rods, at the least because of mild grinding with sandpaper. Because of the reduction of journal diameter, I'd need thicker shells to try to keep the gap between journal and shell surface within spec... right?
I must be misunderstanding what you're saying in that last sentence.

 

[bwringer]

FWIW, you can get a very serviceable digital micrometer from Harbor Freight that reads in MM or inches.
https://www.harborfreight.com/digital-micrometer-63647.html

It's plenty accurate and precise for piffling money. The only real downside to the thing is that the cheap electronics drain the battery. Take the battery out between uses and keep a spare around, and you'll be fine.

All that said, without the measurements a machine shop could do, it's impossible to tell how much you've removed from the crank pin, and it's certainly not round any more, or flat side-to-side.

John Park's advice to employ a machine shop is the best way forward if you want to end up with a reliable engine using this crank. Could you get it to run in your carport with shoestrings and sandpaper? Sure. Would the result be something you can trust on a long trip? Probably not.

Anything can be fixed with enough money, but it's also nearly certain that the best financial decision would be to find another crank that's not damaged. You might have to buy the surrounding engine or bike along with it and scrap the parts you don't need, but you also don't need to care about cosmetics, title, etc.

 

[Guest]

The GS500 crank is a different part number. You'd be taking a risk. I don't know how it's different so I wouldn't know if it matters. Buying a used crank has the benefit of being able to see the crank; buying an engine or bike is assuming that it has a crank that's worth building your engine around.

 

[free99]

Good news guys, turns out my shoestring trick worked pretty well. The crank shop I took it to (Marine Crankshaft over in Santa Ana) was very professional and well equipped. Their measurements after micropolishing gave me a 1.3381" and 1.3380" diameter on the rods, well within spec per the Suzuki factory manual. Even surface, and nicely cylindrical.

$100 got me a magnaflux crack check, precision straightness & measurement of the journal diameters, and micropolishing. Highly recommended.

Anyway, I received two sets of NOS #2 rod bearings. I'll be plastigaging them tonight.

Bwringer, the digital micrometer you mentioned only opens to a max of 1", while the journals are >1.3".

I wound up using the mechanical micrometer set they sell at horror fright as the precision is higher than the digital anyway. If you use them correctly, the manual micrometers are actually pretty spot on, my measurements of the journals varied from the machine shop's by about a tenth of a thou. Just be careful, the hardened carbide tips will scratch/gouge. Doing a measurement of cylindricity involved rotating the crank by 120 degrees and measuring, and measuring for any taper on each journal involved a measurement on two spots for each angle, for each journal. This means a total of 12 measurements, just for the two conrod journals.

 

[free99]

Hmm... so I've reassembled the engine, kept everything clean, greased all bearing surfaces, very thin dab of sealant around the perimeter of the case.

Engine spins freely, seems ok. However, I cannot shift out of a small range of gears. I was careful with the shift forks and such, but I must have made a mistake.

Would anyone have any suggestions on where to look? I wonder if it has something to do with part number 9.

 

[Nessism]

Realize that the transmission won't shift smoothly through all the gears without some rotation of the transmission shafts. Are you turning the output shaft some while trying to shift? If not, you might want to try.

 

[free99]

Hey Ed, thanks for your advice.

In this case, even after rotating the tire as best I can within the range permitted by backlash, the gears stay in their limited selection range.
I'm pretty sure the shift forks are ok/unbent, gear teeth look good. Only thing I can think of is the actual shift mechanism as I had to kind of figure it out from the fiche (part #9).

Oy vey, and I just filled her up with oil. :dispirited: