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....... :whistle:
I would look at moving the engine mounts before cutting pieces out of the cylinders
Quote from: rodneya on October 22, 2020, 03:17:37 PM
I would look at moving the engine mounts before cutting pieces out of the cylinders
^^^^this^^^^
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.
Not a very clear pics.but here goes.
Well if cases are already welded and cylinders cut the only out is weld an edge to hold the water
agreed. you need more surface to seal properly or you'll be chasing it forever.
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.
Thanks.But what if I were to either face the heads or even without facing them use a very thin custom made copper gasket?
not enough surface area to hold it. you need to address the cyls first.
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.
Something like this could work?
https://youtu.be/Zq4l0sj7sbQ
not for long. you need to add area to it :wave:
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.
Quote from: bitzz on October 23, 2020, 02:09:23 PM
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
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.
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.
Maybe off topic, but how will a 4 cyl RD type crank with RH end primary drive hold up at TZ750 power levels?
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/
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.
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.
Template for a 0.4 mm copper gasket.
https://coppergaskets.us/
These guys do custom ones, he did one for me years ago, was really nice. :twocents:
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 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.
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.
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.
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:
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.
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.
I agree the only way out at this point is to rebuild the mating surface with weld, then machine flat.
Copper gasket. Fingers crossed.
maybe im missing something here, but whats going to seal the combustion chamber? :umm:
Quote from: m in sc on October 28, 2020, 11:22:19 AM
maybe im missing something here, but whats going to seal the combustion chamber? :umm:
The O-Ring
This is just to keep the water from leaking outside.
Quote from: mavguy on October 28, 2020, 12:04:34 PM
Quote from: m in sc on October 28, 2020, 11:22:19 AM
maybe im missing something here, but whats going to seal the combustion chamber? :umm:
The O-Ring
This is just to keep the water from leaking outside.
Is the o-ring proud of the copper gasket? Just asking as copper wont squish down like an oring will. O-rings squish flat to the mating surface.
Watch for any potential burning coolant. Will smell sweet as well and burn white.
The o-ring needs to be totally "enclosed" by the groove and the head. Unless the gasket thickness somehow is compensated for, the o rings Will burn.
yup.
you're going to ultimately have to get those cyls modified one way or another. you lift the head with the copper gasket you'll extrude the o-ring in no time.
Is there a chance he could get away with a layer of three bond over the o rings to both close the gap and help prevent the o rings from burning? Assuming it sets air tight.
thats a negative. it either needs to be a full copper gasket or repair the cyl and do it right, you cant hybrid it. the flame front will burn the rtv and o ring right out with that much of a gap filled.
I am in with the sceptical posts of most guys.
It will not work with the copper gasket.
There is a reason why all 3 or 4 cylinder watercooled conversions of RD/TZ based 2cylinder crankcases has either welded cylinders and heads like this one
(https://up.picr.de/39745242ap.jpg)
(https://up.picr.de/39745239kh.jpg)
(https://up.picr.de/39745243fa.jpg)
or with special casted sole cylinders and heads like these
(https://up.picr.de/39745246ie.jpg)
(https://up.picr.de/39745235hp.jpg)
(https://up.picr.de/39745231fa.jpg)
I am myelf in the process of building a 3 cylinder TZ engine and have 2 friends which built 3 and 4 cylinder RD based engined bikes. They used RD/LC cylinder for cost reasons,
(https://up.picr.de/39745359rc.jpg)
Regards Uwe
Agree about any gap with a O ring, immediate failure. You may be better off making both surfaces perfectly flat and spraying Copper Coat on it. I did that with a RD once and it worked ok. Not sure about your compression ratio though.
I would figure out how make o-rings work. To make the copper work you are going to have to bastardize the heads. You already bastardized the cylinders so I'd just keep working on those to make those work with o-rings.
Sorry,
I don't know why but did a double post and deleted the 2nd