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GS450 to 500 swap questions

D

diptenkrom

Forum Apprentice
I have bought some of the parts already. and i am ramping up to doing this swap soon.

I have a 500 cylinder jug and pistons, as well as cams and a badly running 1981 GS450 scrambler build.

I read elsewhere that the head studs from the GS500 were better, so i will be ordering those

My biggest question is the cams. how do i figure clearance for the valves, ;and how do i know what needs to come off the piston to make valve clearance?

i do plan on using GS500 carbs or some other upgrade, and i know there is a mix of gaskets and what not to make this work. any advice would be appreciated. I have been reading about this here and there for like a year, but no real clear answer on the piston to valve clearance that i can find other than it needs to be done.
 
There's no definitive answer about valve to piston clearance. This is because all the parts you are going to use will be already used and the head for instance may have been machined. The safe way is to mock up the top end on the motor with plasticine on the piston(s) and turn it over by hand. Cutting the plasticine with a craft knife will tell you how much clearance you have. Ideally you want at least .060in both sides.
That said, if it's a street motor and the head hasn't been machined the inlet usually measures up around .045 -.050in. If it's only going to be used on the street that is safe IMO.
If it's a race engine or will see track days then it needs the full .060in. Any hot cams will need the pistons machined. And probably better valve springs.
 
Thanks GregT, the bike is in a bike that I am building for a scrambler bike. It will not be doing anything serious, or raced or anything. It was just not running right, and i figure that i am going to tear into it, and the parts are cheap enough, i might as well squeeze a little more out of the bike. This is just a low buck extra bike project that i have been stagnant on since reshimming the valves didn't get it running right. My first bike was a GS500 and i liked the simplicity, but i liked the look of the older UJM bikes and i found the right deal for $500 about 2 years ago, and tinkered for a bit, and now it is something i want to get going. it is not my only bike, but it is part of my "ideal garage" so i would like for it to be reliable. Any added info there would be greatly appreciated. I plan on new gaskets and seals and i have already ordered NOS valves and will be taking the head to the machine shop for trueness and valve work before assembly.

Is there a guide in general on how to do the valve clearancing? i read a few places that the cams really made a difference on an otherwise stock GS450, so i dont want to leave that part out.
 
Once the bottom end is together, mock up the top end. You only need one piston in for a trial assembly.Don't even need rings or pin circlips on it. Don't torque the head down, just a light nip. Plasticine in the valve pockets or at least on the piston crown under the valves. Time up the cams as per the manual and turn the engine over slowly.
Pull the head off and you'll see where the valves have hit the plasticine. Cut it with a craft knife and measure the thinnest point. I use a vernier caliper with a dial gauge attatched but a simple depth gauge will do.
 
first of all, Thanks!

so they wont hit enough to cause any damage like this? i assume i should have the cam caps shimmed to spec first?
do i just use a dremel with a sanding barrel? it sounds like im not removing a lot of material, but should i be real concerned that they will not necessarily be equal on each piston? is there a better way?

also never used plasticine, is plastilina pretty much the same thing? www.amazon.com/Sargent-Art-Plastilina-Modeling-2-Pound/dp/B00FR7TQOM
 
Yes, that stuff looks like it would work. Yes, valve clearances shimmed correctly. Turning it over quietly by hand and not forcing it if things hit is safe. If material has to be removed from the piston crowns, it's best done in a mill.
 
Thanks for all the information! Now i just have to starft taking things apart! hoping to get that done this weekend. would be nice to get to the point of riding this bike in a month or 2... instead of it sitting here for another 2 years
 
LAB3 said:
When I looked into doing that swap on my 450 the folks over on the gs500 board gave me a lot of good advice, you might want to check out what they have to say.

https://gstwins.com/gsboard/index.php
Click to expand...

I have looked around that board as well. I cant find your posts there, what was your username there so i can search?

did you go through with it?

BTW - I finally got the engine pulled this weekend. hope to tear into it sometime this week, valve cover is off, that is alli got done :(
 
I've never did anything on my 450 that deviated from stock just relaying the conclusions I had come to. The position of the exhaust ports between the two frames is about the only thing that separates the two engines.
 
Anyone know if there is a way to add an oil cooler to the gs450 engine? Just a though I had while it is apart, and I live in the south, it gets hot here for a large part of the year.
 
diptenkrom said:
Anyone know if there is a way to add an oil cooler to the gs450 engine? Just a though I had while it is apart, and I live in the south, it gets hot here for a large part of the year.
Click to expand...

It could be done. Two possibilities. A takeoff from the oil pressure sender cover behind the cylinders. I suspect a takeoff made for a GS1000 would work here.
And an oil filter cavity cover from a late GS1150 with the cooler takeoffs would probably work too. I think the bolt pattern is the same.
The concern I have is the oil pump capacity. It's a plain bearing motor and any drop in pressure while filling the cooler on startup could get expensive. No easy way to increase the pump capacity either.
 
GregT said:
It's a plain bearing motor and any drop in pressure while filling the cooler on startup could get expensive. No easy way to increase the pump capacity either.
Click to expand...

I suspect that's the reason why the XJ900 has an oil level light instead of a pressure light. The oil cooler is rather daftly mounted pipes-downward, so it drains when sitting.
Not that it's done the engine any harm in 100K, but owners would have been worried about the light delay on startup.
 
grcamna2 said:
How has your project been going so far 'diptenkrom' ?
Click to expand...

Sorry for the late response... a lot has gone on in my life, but not a lot with the bike.

slowly, lol. I have the motor apart, the head has been machined flat with NOS valves and a 3 angle job. I have put the 500 jug and pistons on, i left th old base gasket on for thickness to be right. i have the plasticine, and i have the valves shimmed, (if i recall i need to remeasure, as i think one is borderline, and the feeler gauge kit i had at tthe time was less complete.) I have all the gaskets and hardware to put it together. the weather has not been friendly, and i have a bit of extra stuff in my shop at the moment. i had to get my GoldWing road worthy as i took a trip on it back in Oct. I also bought a Kawi Concours 1000 with fuel leak issue for a trip hopefully in the late spring, that i will sell afterwards. anyway i am now splitting time i have between the GS450 and the 79 GS1000
i am front end swapping. I came back to this thread to refresh my memory on the GS450, as i hope to put some time into it this coming weekend. Doing the plasticine test should not take more than a couple hours, if i can get a bit of a hand from someone to help me keeep things from moving aroudn too much.
 
diptenkrom said:
I also bought a Kawi Concours 1000 with fuel leak issue for a trip hopefully in the late spring, that i will sell afterwards.
Click to expand...

Are you familiar with the Concours ?
The fuel leak issue you mentioned rings alarm bells !
The carbs on this bike do not have an overflow pipe, often causing hydrolock when fuel leaks, which can cause serious damage.

Steve Sefsick from Florida modified them for customers, adding overflow tubes, hope yours has them.
If your carbs have overflow tubes he probably did them, they will be rejetted and your airbox will likely have a piece of foam in one of the intake holes.

I have one, great bike, but they can have some issues that may spoil your trip if not addressed/checked.
Well known issues are with the Junction box (causing electrical issues), water pump leaking oil, final drive leaking, clutch star spring breaking, and carbs causing hydrolock.
Most of them easily solved.

If you are not familiar with those issues, i can help with info.

Highly recommend Concours guru Steve Sefsick's Youtube channel https://www.youtube.com/@steves3261/videos
And the COG forum https://forum.concours.org/index.php?forums/concours-c10-zg1000-general-chat-and-tech.80/

Hope you bought yours from a COG member that performed the necessary repairs/maintenance and the bike did not hydrolock.
I will add an electronic fuel shut off valve to mine to help prevent this (my carbs do not have the overflow tubes modification)
 
Last edited:
diptenkrom said:
Sorry for the late response... a lot has gone on in my life, but not a lot with the bike.

slowly, lol. I have the motor apart, the head has been machined flat with NOS valves and a 3 angle job. I have put the 500 jug and pistons on, i left th old base gasket on for thickness to be right. i have the plasticine, and i have the valves shimmed, (if i recall i need to remeasure, as i think one is borderline, and the feeler gauge kit i had at tthe time was less complete.) I have all the gaskets and hardware to put it together. the weather has not been friendly, and i have a bit of extra stuff in my shop at the moment. i had to get my GoldWing road worthy as i took a trip on it back in Oct. I also bought a Kawi Concours 1000 with fuel leak issue for a trip hopefully in the late spring, that i will sell afterwards. anyway i am now splitting time i have between the GS450 and the 79 GS1000
i am front end swapping. I came back to this thread to refresh my memory on the GS450, as i hope to put some time into it this coming weekend. Doing the plasticine test should not take more than a couple hours, if i can get a bit of a hand from someone to help me keeep things from moving aroudn too much.
Click to expand...

You're getting it done;one thing at a time.
 
diptenkrom said:
Anyone know if there is a way to add an oil cooler to the gs450 engine? Just a though I had while it is apart, and I live in the south, it gets hot here for a large part of the year.
Click to expand...

The late GS500 (the F models) have an oil cooler from the factory.

There are some other differences between the 450 and 500 engines. The exhaust ports are the obvious ones, but the shifter is different too. There is no transmission gear indicator wiring on the 500....... I think the carb mounting boots are different? I can't remember that last one.
 
Sorry to anyone that was trying to follow my progress, as life happens... there are 2-3 questions in this post it anyone spends the time to read and wants to answer, mostly on fork oil and suspension bushings.

GoldWing got together, but not what i would call complete. It runs and rides great, and have been on a trip or 2 and some general riding around. - love that bike as it is, just need to finish it. whats left - fixing the rear fender mounting and tail light, getting the blinkers working, some sort of headlight/cluster cowl, cleaning up some wiring runs (loom), a different choke cable with mount to make it easier to use, finding a good phone mount that i like for it, redoing a few connections in the loom, adding a resistor or something to make the temp gauge work right, and painting it.

Concours 1000 drove me crazy for a while, but i never got it quite right, and sold it at a break even, I only rode it once like 4 miles :( - those carbs SUCK

The 79 GS1000, i got it running and proved that it is worth working on, but it is back burner until the 450 is back together. - this will be a neo-retro bike with ~06 GSX-R 750 forks and swingarm, and i have a set of CBR F3 wheels to get powdercoated for it. - this one will be going for aesthetics for sure. Gold or burgundy wheels (unsure yet) with factory burgundy tank (when progress here starts, i will make another thread) i hope this one will not take 5 years :(

For the GS450 - i have FINALLY started working on it again (had carpal tunnel surgery last dec, and a few other things happened). with hopes to get it together this month. I tested the head on the 500 cylinders, with the 500 cams and had what seemed like plenty of clearance, unless i am an idiot (more than 1mm). i will probably test this one more time on final assembly to be sure. i plan on honing the cylinders and cleaning up the top of them this week. I also will be installing the piston rings and getting the motor ready for the head. I have swapped the front forks for a set of '81 GS850 ones, with the brakes from the 850 (450 caliper bracket has different spacing) and i have to rebuild the forks, and figure out headlight mounting as the factory mounts might not work. The tubes will go on the forks, but as the forks are not just bigger and longer, the triple spacing is different (wider and taller) they will be loose, so some kind of spacers/holders will have to be figured out. maybe a few small pieces of hose or something will work, if not custom mount brackets are cheap. i got a ProTaper bar with adapters and installed that. Just have to put on grips, and figure out spacing for everything else on the bars, and do a little drilling. i have a set of mirrors off my son's KLX 300, since he swapped to aftermarket ones, so i might put those on, but i have an old mirror, that i think came from an old Magna or GoldWing that is on the left side at the moment.

this all leaves the rear suspension... i didn't want to get some of the cheap apparently hit-or-miss shocks off ebay or amazon, so i ordered a set from a triumph scrambler. they are like 1.5" taller, and have progressive springs, so they should accomplish what i am after, but the bushings are not the right size. i don't have exact measurements yet, but the triumph bushing is like 34mm OD and prob 14mm ID. the length of the metal sleeve matches though. I have not found any usable bushings yet, since i need what is about 34mm OD to 12mm ID and not finding that from anyone online easily. I am contemplating getting 12mm stainless sleeves and filling the top/bottom mounts with either pourable polyurethane or Window Weld or the like. does anyone have any experience in this area that can help?

Also, the GS850 forks call for 10wt fork oil, some people use heavier. I am about 215lbs, and want to do some light off-roading with this bike (the purpose of the budget scrambler to begin with) - would you guys recommend sticking with the 10wt, or going 15wt, or some sort of blend of the 2? After riding i will determine if adding cartridge emulators will be something to spend money on later.

front wheel is from GN125, and the rear wheel and brakes will be swapped in from a GS550, so disk swap in the rear - and i have new bearings (frt and rear) and the cush drive that came with the rear wheel. I also have the GS1000 and will probably use the right side of the exhaust and try to make a 2 to 1 right side exhaust as the curent setup was chopped short and mounts low, i want a higher right side single mount.

Sorry for the wall of text, but this has been a long time waiting, and a lot has happened in the last little bit, and hopefuly in the next ~month, as i want to ride this thing in Mid Sept.
 
I also have a GS450 which I want to swap-in larger pistons(75mm custom pistons)and use the GS500E cylinders.
I will be making my order for a pair of custom pistons in a few days,and JE Pistons comes highly recommended.

The way I will get the pistons made: I will get custom pistons of 75mm with the exact dimensions of GS500E pistons,although they will be made with the exact same crown/dome shape of the GS450.
The cylinder block from the 500E is .050" taller than the GS450 cylinder block and the 500E ring stack on the pistons has more height to it.
The GS500E cylinder head will not work in the GS450 frame because of the orientation of the exhaust ports(the 500E ports would exit right into the GS450 frame tubes !)plus the GS500E head/combustion chambers are 'closed chamber design' which brings the compression up(9.2:1)a bit for the GS500E engine,considering the small crowns on the GS500E pistons.
The GS500E pistons will not give you enough compression when using the GS450 head/combustion chambers,as they require the more peaked domes of the GS450 pistons,which will give you 9.0:1 (stock GS450)compression ratio.
The GS500E pistons will give you much lower compression than that,when using the GS450 head;you'll lose performance.
I measured this out and recognized my need for custom pistons.
 
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