A Katana................in here................?????

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garry55
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Re: A Katana................in here................?????

Post by garry55 »

dgoodsy wrote:cool! (not the waiting part, but the part about raising the exhaust ports.)

Being a noob to modifying 2 strokes I had to google how raising exhaust ports affects performance. I read that it trades off a little low end grunt for some top end power. What is your plan for an exhaust system?
I am going to run a 3-1 system to try and keep the "stealthy 2-stroke" look.
Garry


I'm addicted to brake fluid, but I know I can stop anytime.
rngdng
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Re: A Katana................in here................?????

Post by rngdng »

I have a spacer plate (3mm lift with the extra gasket) under by jugs, and with my Jemco pipes, and 34mm VM carbs, and 3 mm removed from rear piston skirts, I am putting about 80 HP on the ground, revving hard up to 8K. If you raise the ports, and use a 3 into 1, you're gonna break even and basically get stock power. 3 into 1 typically only revs to about 6K. Don't get me wrong, it'll still be fun.


Lane
If you stroke it more than twice; you're playing with it.

Too many bikes, too much time, ENOUGH SPACE, FINALLY! Never enough money.........
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garry55
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Re: A Katana................in here................?????

Post by garry55 »

you got it in one, Lane :up:

the idea is to get standard GT750 power using the 3-1 system.
Garry


I'm addicted to brake fluid, but I know I can stop anytime.
rngdng
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Re: A Katana................in here................?????

Post by rngdng »

garry55 wrote:you got it in one, Lane :up:

the idea is to get standard GT750 power using the 3-1 system.


I hope you are using an MAB cylinder. That's what I have, and it works well.



Lane
If you stroke it more than twice; you're playing with it.

Too many bikes, too much time, ENOUGH SPACE, FINALLY! Never enough money.........
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garry55
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Re: A Katana................in here................?????

Post by garry55 »

no - I am using a "J" motor - slide carbs and all................. :clap:
Garry


I'm addicted to brake fluid, but I know I can stop anytime.
rngdng
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Re: A Katana................in here................?????

Post by rngdng »

The slide carbs area must.



Lane
If you stroke it more than twice; you're playing with it.

Too many bikes, too much time, ENOUGH SPACE, FINALLY! Never enough money.........
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garry55
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Re: A Katana................in here................?????

Post by garry55 »

I have 2 sets of slide carbs - 32mm and 34mm. Will probably save the 34's for the track bike.
Not looking for out-and-out performance from the road bike.
Garry


I'm addicted to brake fluid, but I know I can stop anytime.
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tz375
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Re: A Katana................in here................?????

Post by tz375 »

Stock zinc 32s or real ones??

Stock OEM carbs are heavy and long but they are less tall than aftermarket carbs. Almost all 32mm and larger carbs are too tall to clear the clutch side crankcase. There are some 34mm small body snowmobile carbs around that clear and there are other options available. Some guys mill the early block to raise the downdraught angle. Others use angled carb adapters. Another fix is to cut a section out of the top crankcase half and weld it back in as a concave curve.

The last option - for lazy people is to let the carb drain bolt rest on the crankcase but that tends to cause fuel frothing and related problems.
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garry55
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Re: A Katana................in here................?????

Post by garry55 »

I have one set of stock carbs and one set of Keihins. The stock carbs should fit OK - I haven't tried the Keihins yet. Also have a couple of sets of the later stock CV carbs which may be OK for road use?
Garry


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tz375
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Re: A Katana................in here................?????

Post by tz375 »

Correct. BS40 carbs are OK up to around 100HP as per Bob Prior. His makes around 95 RWHP IIRC and that's on stock OEM carbs
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garry55
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Re: A Katana................in here................?????

Post by garry55 »

In which case I will build the later motor for this project and utilise the stock CV carbs - I think they transition better than slide carbs for road use.
The XR11/73 project can run the slide carbs as that is primarily for track use.
Garry


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tz375
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Re: A Katana................in here................?????

Post by tz375 »

For the street, my preference is late 72, 73 or 74 barrels ported on the exhaust side to better than MAB specs with stock (but cleaned up) intake timing. Tests show early motors made more torque and analysis suggests that the later intake timing hurts more than the exhaust timing helps, so go for both - port and older block.
rngdng
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Re: A Katana................in here................?????

Post by rngdng »

It's your bike...do what you want. I rode a 72 with a 75 engine using the 72 carbs and it was a wheelie machine. Power wheelies were easy, and made me laugh until the rear tire blew out....another story. My bike, as is, does power wheelies if I want it too, but I'm not a wheelie king, so I don't do it much.


Lane
If you stroke it more than twice; you're playing with it.

Too many bikes, too much time, ENOUGH SPACE, FINALLY! Never enough money.........
User avatar
garry55
Yeah Man, the Interstate
Posts: 629
Joined: Wed Jan 01, 2014 2:04 pm
Country: UK
Suzuki 2-Strokes: GT750 hybrids (x2) RGV500

Re: A Katana................in here................?????

Post by garry55 »

you used early carbs on a later motor?
are the inlet manifolds compatible? (I don't have a set of post-J/K manifolds to check).
Garry


I'm addicted to brake fluid, but I know I can stop anytime.
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tz375
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Re: A Katana................in here................?????

Post by tz375 »

Yes. All late J and K on barrels had the same diameter intake stub and will take K inlet rubbers which allow you to fit J/K slide carbs on any motor.

J/K slide carbs have a 43mm outlet OD which is the same as regular VM34, TM38 etc. TM32 are 40mm OD as are small body 34s but they can be sleeved up to fit into a BS40 intake rubber. Lane (rngdng) let me into that secret.
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