Gas Gas Rebuild

Ichy · World Chat Champion Joined: 15 Jul 2005 Karma :

Loads

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I'll upload some of the pictures later.
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Ichy · World Chat Champion Joined: 15 Jul 2005 Karma :

Having stripped it all down the only part of the gearbox that looks like it needs work was the gear selector. I guess with this kind of bike that it is a little bit vulnerable.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P1141396Copy.jpg

I'll give it a whack and see if I can straighten it out.

Cases were all stripped using the old version of nitromors. It works well but is damn messy and burns when you get it on your arm Rolling Eyes

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https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P1141381Copy.jpg

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P1141383Copy.jpg

There was a bit of damage to the clutch and generator cover that I had to work out. I didn't want it to be perfectly smooth so it took a bit of time to get right. I'm pretty happy with the results.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P1141393Copy.jpg
https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P1141394Copy.jpg

I sourced a litre of high temperature paint locally. It costs about £15 for a litre, way to much for this engine but I have plans for the future!
https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P1141392Copy.jpg

All the bits painted. Unfortunately my mini spray gun decided to play up so I couldn't get enough coats of the silver on the cases. I'll order another one and finish the paint next week.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P1141391Copy.jpg

Pre assembled to check it out.
https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P1141389Copy.jpg

All the bits that needed replacing, clutch, reed valves, piston and rings, are sitting on the bench waiting. I'm still waiting for the bearings and seals to turn up, hopefully early next week. I priced up all replacement bolts and will put an order in later.
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woll · World Chat Champion Joined: 01 May 2010 Karma :

i'm getting messed about by the garage. I shall be paying them a visit tuesday kick their arses and get the bits out of my tools box.
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Current Bike- Suzuki DRZ400 SM K6
Previous bikes - Derbi Senda Xtreme50r, Honda CBR 125, Kawasaki ZZR 250, Yamaha DT125R, Suzuki Bandit 600, Gas gas ec 250, Honda CBR600FW
Damaged spleen, damaged kindey, 2 popped lungs, 2 broken ribs, broken face, broken wrist and 5 back fractures... remember kids walls hurt

Ichy · World Chat Champion Joined: 15 Jul 2005 Karma :

Ichy · World Chat Champion Joined: 15 Jul 2005 Karma :

I had a couple of hours free this afternoon and so I did a bit more work on the engine.

First I sorted out all the replacement bits I'd brought.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P1271508Copy.jpg

I did quiet well with some of the bits. A new CR250 piston, teflon coated(?) was won for 1p. I did have to travel 80 miles to pick it up but still worth it Laughing

. New rings were £5 and the second hand reed block was £12. I've also won a set of CR250 clutch plates for £10 to replace the worn ones I have. The bearing and seals worked out at less than £80. All decent brands and it includes the bearings and seals for the wheels.

Next job was to finish off painting the engine. I had to give up last time due to a broken spray gun. I saw a cheap one on Ebay for £11 and decided to give it a go, at that price it's almost disposable.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P1271503Copy.jpg

I didn't want to spray inside and the weather today was completely unsuitable for outside spraying but I decided to give it a go rather than wait another week. I put the engine cases in the oven for 20 minutes at 50 degrees to help the paint out. I then hung it from a beam under the car port.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P1271500Copy.jpg

The gun worked fairly well other than the airflow being just a bit too powerful even with the regulator set to 10PSI. It just doesn't seem right so I'll have to check it out before I use it again. Still, engine is painted.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P1271507Copy.jpg

Just to drag it out even longer I plan to spray lacquer on over this weekend.

Only other thing done was to assemble the cylinder, it has literally taken 3 hours Shocked

. The power valve was one of the few parts that were removed when I picked up the bike. Looking through the bits that I had I realised there were a few missing, all the expensive ones Rolling Eyes

. Woll was good enough to sort through his toolbox and found most of them. Strangely enough one of the parts he couldn't find was the control rod for the power valve. He couldn't even remember taking it out! I was going to make a new one until I realised they were only £3 from Gas Gas. Delivered next day.
There was one spacer missing but I managed to make one out of some bar I had using a hacksaw and a file to shape it. I really need to get a lathe.
It finally became time to fit the exhaust port thing. I have no idea why but the exhaust gasket I had was completely wrong, some things never change. I always have a few sheets of gasket paper so knocked one up. A bit roughly but functional.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P1271511Copy.jpg

All done, with a fully working powervalve.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P1271514Copy.jpg

All being well I should start assembling the gearbox tomorrow. Should be fun, I didn't take many photos when I ripped it apart.
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HD · World Chat Champion Joined: 16 Dec 2009 Karma :

Isn't it a bit awkward when you turn up to buy something for 1p? Laughing

Also, is the whole engine the same as the cr250?
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Rusty '02 Vito Camper + CBR600F3

Ichy · World Chat Champion Joined: 15 Jul 2005 Karma :

Certainly is embarrassing walking up to someones house with a penny in your hand. Laughing

. Thankfully the guy was emigrating So just laughed and gave it to me. I offered him a fiver but he didn't want it. He also gave me a brand new reed block off a CR250, pity it doesn't fit.

Only a few parts off the CR fit, and not all of those are perfect. The piston seems to be one of the few that is a straight swap. The clutch plates are thinner on the GasGas but you can get a new thrust washer to get the overall size correct when fitting CR plates.

For reference the bearing were sourced from Bearing Boys https://www.bearingboys.co.uk/Bearings-1005-c?gclid=CIuY67v48K0CFcxofAodpHXkrg.
All good quality stuff from stock although delivery was a little slow.

The seals were from Superseals https://supaseal.co.uk/oilseals.htm. Bargain price for seals in a material, FPM, that is comparable to viton. Pretty helpful.
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woll · World Chat Champion Joined: 01 May 2010 Karma :

Looking grand Thumbs Up

. I still don't understand where' the rod was but it never came out of the engine when I stripped the top end so who knows. Wonder what the bike will be like with a fully working p/v Thinking

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Current Bike- Suzuki DRZ400 SM K6
Previous bikes - Derbi Senda Xtreme50r, Honda CBR 125, Kawasaki ZZR 250, Yamaha DT125R, Suzuki Bandit 600, Gas gas ec 250, Honda CBR600FW
Damaged spleen, damaged kindey, 2 popped lungs, 2 broken ribs, broken face, broken wrist and 5 back fractures... remember kids walls hurt

Ichy · World Chat Champion Joined: 15 Jul 2005 Karma :

Well the cold weather really has some uses Laughing

. I fitted the bearings today and actually forward planned enough to leave the bearings outside over night. I warmed up the cases in front of the fire and the bearings just fell in.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P2031528Copy.jpg

Next the seals and the crank. I left the crank in the freezer for a hour and it dropped into the bearing nicely. The seals were a bit tight, they could of done with warming up a bit, but they went in ok.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P2031529Copy.jpg

Finally a dummy run with the gearbox bits. I managed to remove the mark I made to help align the selector drum so it will take a bit of trial and error to ensure it all works ok.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P2031530Copy.jpg

Given the choice I would of replaced the selector forks, there is a bit of wear on them. I can't find a good used set in the UK and new would cost around £45 each. I might go ahead and get a set from America for £50, I'll have to see. It'll slow things down, if that was possible, but I could start work on the frame and wheels.
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Ichy · World Chat Champion Joined: 15 Jul 2005 Karma :

I really wasn't happy with the selector forks. They might have been fine but I didn't fancy having to split the cases again if they did play up.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/SDC11018Large.jpg
https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/SDC11020Large.jpg

So I asked around at work until I could find someone that would let me loose on their milling machine Laughing

. I tested the material of the selector and it came back as roughly the same as an high tensile bolt. The hardening hardly seemed worth while since it was more or less just on the surface. I shouldn't complain, it makes it easier to machine. Firstly I measured the pin at 6mm x 7mm then they each one was stuck it in the vice on the milling machine and the pin clocked up to ensure that it was vertically aligned before finding the center. The datum was set on the dro and the pin machined off the selector. They were then realigned to the datum and drilled through with a 5.9mm drill before being reamed out with a 6mm reamer. The only dowels I could find were 13mm long, 10mm would have been perfect but that's life. Warmed up the selectors and the pins popped in nicely with a bit of persuation.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P2161826Large.jpg

I've cut one off at 7.5mm for now just to check the fit. Looks good. I just need to grind the face flat and put a small chamfer on it.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P2161827Large.jpg

Hopefully once they are finished there is nothing to stop the cases going back together. I do have some stud lock but I might put a bit of braze on them as a 'just in case'. Not sure at the moment.
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P. · Red Rocket Joined: 14 Feb 2008 Karma :

Some skills of the BCF crew are hard to fathom.

I can barely make toast... Laughing

CHR15 · Turbo nutter bastard Joined: 14 Jun 2008 Karma :

would brazing them not alter the hardness?
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Ste: I'm not entirely sure how you'd go about verbally abusing someone with a potato but I'm sure it's possible.

Ichy · World Chat Champion Joined: 15 Jul 2005 Karma :

Your right Chris and it is why I'm unsure of which way to go with it. Some of this might be wrong in which case I'll learn the hard way Laughing

.

The temperature for brazing with brass rod is around 800c which is close to the tempering temperature of medium carbon steel. This means that there is a opportunity to quench the part but I'm concerned that since the dowels are through hardened already that they might fracture.

This is were I go way outside my knowledge but my next thought was to braze the bits, let them cool naturally and then case harden them with some carbon powder stuff that I have.

I guess another choice would be to solder the parts together. It's not a structural joint, just a safety net. Not something I've ever done but it would be interesting to see if it works.

At the moment I will probably just go with the stud lock and wait until I can speak to one of the metallurgists at work. Maybe I'm going over the top but I don't fancy one of the pins dropping out Shocked

. All fun!

Just another thought but the obvious thing is to drill a load of holes and stud lock some dowels in them. When its set I can attack them to see how easy it is to pull them out. I still want to try soldering one though Laughing

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steven_191 · Nearly there... Joined: 31 May 2009 Karma :

Really those studs should never fall out even if they do move.

Have you ever seen the bearing lock stuff that loctite do?
Apparently its the same stuff used in aerospace. They cut a hole for the bearing that's is exactly the size for the bearing to slot in and fix it with bearing lock to negate the need for heating the metal to stretch it as this could in effect move it.
I've used a bit recently and it is good. Not sure how it differs from their thread lock but I would just go for the most permenant lock they have and use that.
Although if its a tight fit already would you need to? You could always just get a slim punch and knurl the edge of the selector into the side of the stud providing it doesn't hinder the gear selection of course.

Good work there Thumbs Up

Ichy · World Chat Champion Joined: 15 Jul 2005 Karma :

Thanks for that. You know how it is, why use a toffee hammer when you have a sledge hammer in the shed!

Like I said, I think I'm being over cautious.
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reggie · Spanner Monkey Joined: 22 Dec 2009 Karma :

whay the change of bering in the flywheel side or do the older ones just run ball berings nor a roler one
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Ichy · World Chat Champion Joined: 15 Jul 2005 Karma :

Bearing are the correct ones.

I found some Loctite 648 in the garage so tried that. Perfect! I should have the engine built up tomorrow giving the chance to move on to the wheels.
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woll · World Chat Champion Joined: 01 May 2010 Karma :

MOAR!
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Current Bike- Suzuki DRZ400 SM K6
Previous bikes - Derbi Senda Xtreme50r, Honda CBR 125, Kawasaki ZZR 250, Yamaha DT125R, Suzuki Bandit 600, Gas gas ec 250, Honda CBR600FW
Damaged spleen, damaged kindey, 2 popped lungs, 2 broken ribs, broken face, broken wrist and 5 back fractures... remember kids walls hurt

Ichy · World Chat Champion Joined: 15 Jul 2005 Karma :

Can't be bothered. Neutral

Engine is built and the bike is being stripped down for cleaning and what ever else is required. I'll send you a picture of the shiny engine, might even be worth selling by itself and then break the rest. Thinking

I want a 70's or early 80's bike to play with.
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P. · Red Rocket Joined: 14 Feb 2008 Karma :

garth · World Chat Champion Joined: 15 Dec 2004 Karma :

I'm just here expressing an interest if you're thinking about getting rid.

That and I have a 1977 5 Speed ss50 if that counts as interesting. It has a powdercoated frame and things, but needs a top end.
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HD · World Chat Champion Joined: 16 Dec 2009 Karma :

1991 Bandit 400 freshly rebuilt?...

Guess not Sad

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Rusty '02 Vito Camper + CBR600F3

HD · World Chat Champion Joined: 16 Dec 2009 Karma :

1991 Bandit 400 freshly rebuilt?...

Guess not Sad

____________________
Rusty '02 Vito Camper + CBR600F3

Redoko · World Chat Champion Joined: 04 Nov 2009 Karma :

Ichy · World Chat Champion Joined: 15 Jul 2005 Karma :

I probably didn't give the right message. I cannot see the point of posting on the project since it is taking way too long and there isn't much interest. I'll finish it off and sell it on. That said this is the current state of the engine.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P3102049Medium.jpg

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P3102048Medium.jpg

It does need a bit of a clean.

Rest of the bike is being stripped and worked on as I find the time. It helps that I have a new garage buddy. More of an hinderance than a help since she keeps stealing bolts but I'm sure that she will work out what to do with them in the future.

https://i93.photobucket.com/albums/l41/marki_03/Gas%20Gas/P3102051Medium.jpg
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