2 up 1 down GT crank

Suzukidave · Post by **Suzukidave** » Fri Jul 31, 2009 5:01 pm

Anyone have any thoughts good or bad about the thought of setting up a GT 750 crank this way with the the center 180 degs from the 2 end throws ?

pjmcburney · Post by **pjmcburney** » Fri Jul 31, 2009 6:54 pm

Suzukidave wrote:Anyone have any thoughts good or bad about the thought of setting up a GT 750 crank this way with the the center 180 degs from the 2 end throws ?

Hey Dave,

Interesting idea - sort of like an early Laverda triple.

Couple of things I reckon might be a drama:

Balance/vibration - without careful balancing and/or addition of some counter-balance weighting it would vibrate like mad, although it should negate the rocking-couple but you'd have to lose some smoothness.

Responsiveness - would it be more difficult to 'spin' up an engine with the weight of two pistons fighting one?
I dunno, I'm just shooting the breeze, only putting one together that way would really give you the answers you're looking for.

On the same subject, I'm getting Brett to rebuild some RG500 cranks for me for my RG project later in the year.

He rang me this week to tell me he has to restore the phasing between the cranks because they were 20 degrees apart

- could this have been an attempt by a PO of a 'big-bang' RG500? Has anyone heard of this for RG's?

I'd be interested to find out the degrees between splines on the disc-valve shafts. It would be very easy to move, say, the rear discs around one tooth on their spline and adjust the crank phasing to suit...

Cheers
Paul

Suzukidave · Post by **Suzukidave** » Fri Jul 31, 2009 7:02 pm

Thanx Paul for the response , this is just what i am looking for . My deal is with the reeded , injected engine i am putting together for the project bike would be easier to setup with the Micro Squirt ECM if the engine were a twin .

tz375 · Post by **tz375** » Fri Jul 31, 2009 7:24 pm

Dave,

EVERYTHING would be easier if it were a twin.

Suzukidave · Post by **Suzukidave** » Fri Jul 31, 2009 7:35 pm

So any other thought on the subject Richard ?

tz375 · Post by **tz375** » Fri Jul 31, 2009 9:41 pm

Dave,

I'd just leave sequential distribution alone and go for batch firing. It avoids all the fancy timing calculations for a start and I suspect from our earlier discussions that timing is not so important - especially on a reed 2 stroke.

2 up, 1 down would have a terrible primary balance unless you were to add a 4th cylinder on the left side instead of the ignition and water pump cover. You would be able to use a simple ignition arrangement too.

That, is the right answer - a big bang 4 cylinder with GSXR 6 speed trans in a set of billet cases.

Obviously something like a MOTEC M400 would do the job, but at a somewhat higher price point.

Or are M/S selling a sequencer board as an add-on yet?

No. I'd go for firing all three injectors simultaneously if that's an available option.

pjmcburney · Post by **pjmcburney** » Sat Aug 01, 2009 4:27 am

tz375 wrote:add a 4th cylinder on the left side instead of the ignition and water pump cover.

Hmmm...

I've been looking at my spare cases and barrels with just such a thing in mind, lately.

How hard can it be?

If Alan Millyard can make a V12 out of a Z1300, then a four cylinder GT is a definite possibility.

Where's my hacksaw...
Cheers
Paul

Suzukidave · Post by **Suzukidave** » Sat Aug 01, 2009 4:30 am

You just need to send these guys a nice fat check Paul http://www.mattoonmachine.com/Billet_Cases.html

Buffalo-guy · Post by **Buffalo-guy** » Sat Aug 01, 2009 9:39 am

Those engine cases are works of art!! The thought of a four cylinder buffalo make my saliva gland work overtime. A rather lofty cost to set up a program to whittle that out of a lump of recycled beer cans, I suspect. Does bring up some interesting visions though. Makes me wonder what Shannons friend in Aus would do on Lake Gardner with a monster like that. OOOO baby!! I have to go to the washroom now. Cheers.
Fred

ja-moo · Post by **ja-moo** » Sun Aug 02, 2009 10:58 am

The Suki's have a pretty robust tranny, but when making a big bang motor, remember that you are doubling or tripleing the power pulse through the tranny. A grear made for 20 hp, is now pushing 40 through it.

Suzukidave · Post by **Suzukidave** » Tue Aug 04, 2009 7:01 pm

If we had just a redesigned top case so some nice snowmobile cylinders would bolt to it it would be perfect

tz375 · Post by **tz375** » Tue Aug 04, 2009 11:07 pm

Dave,

Those triples come in a range of bore spacings, so you can fit a set of single cylinder MX top ends for an 1800cc triple. But don't forget the billet 74mm or 84mm crank and billet transmission to finish it off.

So that would be:
Cases $2,500
Trans $2,500
Top ends $1,500 (that's a guess)
Billet Crank $1,000
Billet Throttle bodies $1,500
MoTEC M400 EFI/ECU $4,500
Data Logger say $2,500

was anyone keeping a count there?

Suzukidave · Post by **Suzukidave** » Wed Aug 05, 2009 6:05 am

I was thinking a bit more of a budget useing the stock bottom cases , GS750 transmission , billet top case 1500$ ? and top it off with some ebay jugs and pistons from a snowmobile so maybe more like $2500~3000 for the motor

tz375 · Post by **tz375** » Wed Aug 05, 2009 11:12 pm

OK, how about a set of billet cases to take a GSXR transmission (short, stacked and available - like a young lady I used to know

).

The billet cases could be set up to take say a modified Polaris triple XCR800 crank and a set of XCR800 VES jugs canted forwards so that the crankcase reeds clear the trans. They could also be angled backwards with front facing carbs and reeds.

The primary drive would still be a problem, but nothing too hard to work out.
maybe try something similar to a GT750 to keep the trans centralized. That would be wider than an H2 design, but tidier.

It could use the stock XCR ignition and carbs for ease of use and maybe sling an electric foot underneath. It should have a Davis Craig electric water pump for simplicity.

Think of it as a 200HP XCR800 with GSXR trans.

tz375 · Post by **tz375** » Wed Aug 05, 2009 11:45 pm

And before I forget, how about setting it up with a pair of modified Rotax twin cranks with new center drive. Use two pairs of DFI top ends for 1200cc of clean efficient, explosive 2 stroke power.

For a cheaper alternative, use a set of Triple Arctic Cat ZRT Thundercat top ends - only 900cc but lots of power.

The possibilities are endless.

I have an angle grinder, dremmel and electric drill - does that constitute a low cost machining center for the cases, or you think I need something more sophisticated?

Seriously, we need a good CAD/CAM guy to draw this up and get it estimated on a CNC mill.

2 up 1 down GT crank

2 up 1 down GT crank

Re: 2 up 1 down GT crank