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TZ/RD 750 Project help

Started by mavguy, October 22, 2020, 01:12:23 PM

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teazer

They are not exactly cheap though....

Then neither are projects like this one....

And where's the challenge in that?  Built not Bought, as they say.  Some of us like a challenge.

sav0r

I think the best solution is to just weld them up, get them surfaces, and move on. Whomever does the welding just needs to keep porosity low. They can always be touched up with epoxy if there is some porosity on the mating surface.
www.chrislivengood.net - for my projects and musings.

Dvsrd

Maybe off topic, but how will a 4 cyl RD type crank with RH end primary drive hold up at TZ750 power levels?

Striker1423

Quote from: Dvsrd on October 23, 2020, 05:28:47 PM
Maybe off topic, but how will a 4 cyl RD type crank with RH end primary drive hold up at TZ750 power levels?

My guess is about as well as a V-Max 4 crank. Actually, probably a lot better lol.
https://www.snowmobileworld.com/threads/crank-twist-on-vmax4-800.35376/

rodneya

Quote from: teazer on October 23, 2020, 03:59:54 PM
They are not exactly cheap though....

Then neither are projects like this one....

And where's the challenge in that?  Built not Bought, as they say.  Some of us like a challenge.

You still have to build it, you just have a range of aftermarket parts to choose from that are able to handle the added power.

teazer

Quote from: Dvsrd on October 23, 2020, 05:28:47 PM
Maybe off topic, but how will a 4 cyl RD type crank with RH end primary drive hold up at TZ750 power levels?

That's a good question.  TZ750 takes power from between the two cranks IIRC.  Eqach as a coupling gear that holds them in synch, but it's two short cranks, not one long one.

On 180HP triple sleds, power is taken off the end of the crank, but the PTO end is pretty chunky and typically has a double row bearing to reduce shaft whip.  The Mag end is also typically pretty beefy and again uses a double row bearing.

Those are viable options with say a bolt on end bearing holder. 

mavguy

Template for a 0.4 mm copper gasket.

m in sc

https://coppergaskets.us/

These guys do custom ones, he did one for me years ago, was really nice.   :twocents:

Jspooner

Quote from: mavguy on October 26, 2020, 02:00:50 PM
Template for a 0.4 mm copper gasket.

I don't understand how that is going to increase the surface that has been removed from the cylinders though? I would figure out how to leak test your idea before moving forward. I just don't see it working though. I have one of these top ends on my street bike and run it the way it is meant to be run with no issues, I would not change that design.
"Just quit brain fucking it and get it done"

teazer

Just a thought, but could you weld up the inside of the barrels at the mating flange and weld it flat and then do the same on the heads and cut a new O ring groove for a slightly shorter O ring - basically move the ring groove inwards away for the face that was machined for clearance.


m in sc

Quote from: teazer on October 26, 2020, 05:24:01 PM
Just a thought, but could you weld up the inside of the barrels at the mating flange and weld it flat and then do the same on the heads and cut a new O ring groove for a slightly shorter O ring - basically move the ring groove inwards away for the face that was machined for clearance.
this what i think all of us were trying to say above.  I still think its the best way, but of hes hellbent on trying to run it as it is and run a copper gasket.. he might get lucky.

Jspooner

Quote from: teazer on October 26, 2020, 05:24:01 PM
Just a thought, but could you weld up the inside of the barrels at the mating flange and weld it flat and then do the same on the heads and cut a new O ring groove for a slightly shorter O ring - basically move the ring groove inwards away for the face that was machined for clearance.

I was actually thinking the exact same thing. Seems like it would take some very careful welding and re-machining but I think it would work. I just don't see the copper gasket thing working. I can't think of any water cooled engine I've seen that doesn't either use some type of an o-ring or fiber/metal type gasket.
"Just quit brain fucking it and get it done"

m in sc

i had a copper headgasket on the lc before I recut the domes. yeah, it blew hot coolant all over my right leg about 9 years ago.  :taz:

pdxjim

Quote from: Jspooner on October 26, 2020, 07:26:13 PM
I was actually thinking the exact same thing. Seems like it would take some very careful welding and re-machining but I think it would work. I just don't see the copper gasket thing working. I can't think of any water cooled engine I've seen that doesn't either use some type of an o-ring or fiber/metal type gasket.

As I mentioned above, pretty common mod on LC's is to o-ring the combustion chamber, and seal the waterjacket with Threebond.

Almost ready to fire up my LC set up like this ... we'll se if it holds water.
Wasting time on 2T forums since the dawn of the internet. '89 TDR250, '13 300xcw, '19 690smcr, '56 Porsche 356A

Jspooner

Quote from: m in sc on October 26, 2020, 11:02:56 PM
i had a copper headgasket on the lc before I recut the domes. yeah, it blew hot coolant all over my right leg about 9 years ago.  :taz:

There's the OPs answer right there.
"Just quit brain fucking it and get it done"