TZ/RD 750 Project help

[mavguy]

Folks been working on my RD 4 cylinder with TZ750  cylinders conversion. To fit the cylinders in the tight space, had to shave off a wee bit of the sides of both cylinders and heads.Problem is since these cylinders use the O-ring instead of a gasket ,one side won't have enough space/grove left for the O ring to fit leaking water.The option which comes to mind is:
1) use a custom copper gasket like the RDs.
2) use a sealant like loctite SI 587 on the shaved side.
3) suggestions from 2SW members for a way out.......

[rodneya]

I would look at moving the engine mounts before cutting pieces out of the cylinders

[Jspooner]

I would look at moving the engine mounts before cutting pieces out of the cylinders

^^^^this^^^^

[pdxjim]

What they ^ said.



I got rid of the headgaskets and did an o-ring conversion on my LC cylinders/heads

Combustion chambers are sealed with o-rings, and the water jackets are sealed with Threebond or RTV.

Garrett at gra2strokes.com assembled the topend, so I'm not sure exactly what he used

Post some pics of your project please.

[mavguy]

Not a very clear pics.but here goes.

[edgefinder]

Well if cases are already welded and cylinders cut the only out is weld an edge to hold the water

[m in sc]

agreed. you need more surface to seal properly or you'll be chasing it forever. 

[sav0r]

Yeah, create a fair amount of surface area then have it surfaced. Find somebody good to do the surfacing, it will have to be pretty flat.

[mavguy]

Thanks.But what if I were to either face the heads or even without facing them use a very thin custom made copper gasket?

[m in sc]

not enough surface area to hold it. you need to address the cyls first.

[teazer]

That set up will not hold water, so the choices are:

Start again and make the combined crankcases wider and source a new pair of barrels. OR

Turn the pair of barrels into one monoblock and do the same with the heads.  You will have to clamp the parts and pre-heat them to minimize distortion. It may not work, but I don't see a way to get individual heads to seal with no surface to seal against.

That issue is why Yamaha made the 750 barrels and heads narrower than 350 parts so they could make the motor a little less wide, but this one looks like it is too narrow.

It might be possible to machine either the barrels or heads so that the combustion chambers still seal with stock O rings and the water jacket is sealed with a copper gasket. 

Take that idea one step further.  Machine the heads down by slightly less than the thickness of the custom copper head gasket and then machine out the combustion chambers to take Banshee domes which will sit proud of the lower head surface. The copper had gasket would have to be custom cut with "bores" large enough to clear the outside edges of the domes.

I have a GT750 head that was modified like that.  The domes sit lower than the lower face of the head and protrude through the gasket to seal against the top flange of the bores and the copper gasket is just there to keep the water in place.

Even with that set up, you don't have a lot of surface left to seal against.

I tried something similar when I wanted to graft Polaris XCR800 barrels onto a GT750 crankcase but bore spacing is too tight and would have left paper thin (or non existent) transfer port outer walls, so that would have required a crank redesign and new crankcases, so at that point I decided it might be simpler to grab a complete XCR motor and mate it to the back half of a GSXR crankcase for the transmission.  That's how project insanity takes off. 

[mavguy]

Something like this could work?
https://youtu.be/Zq4l0sj7sbQ

[m in sc]

not for long. you need to add area to it 

[bitzz]

Soooooooo I've heard tell of this crazy fella that thinks the answer is 4 Banshee 6 port jugs on a TZ bottom end.
It runs. I'm told it'll do 250HP all day long. I wanna see it.

...it involves an adapter plate between the jugs and the block. Four Banshee jugs is wider than two RD-LC jugs so MAYBE he's using the plate to shift the bore centers.

[rodneya]

Soooooooo I've heard tell of this crazy fella that thinks the answer is 4 Banshee 6 port jugs on a TZ bottom end.
It runs. I'm told it'll do 250HP all day long. I wanna see it.

...it involves an adapter plate between the jugs and the block. Four Banshee jugs is wider than two RD-LC jugs so MAYBE he's using the plate to shift the bore centers.

No need to reinvent the wheel. Mattoon machine makes billet cases for a 4 cyl engine using banshee parts. I think it is called a 20 mil Cougar