42 MM Mikuni Side Draft carbs

Jerry C · 03-19-2003

I have a nice pair of 42 MM Mikuni 1V side draft carbs. I am thinking about building 2 intakes and installing them on my gt. Do you guys think this is too much carb for a 1.9 I dont mind if I loose some torque at the lower RPM, but I still want to be able to drive it on the street. Am I nuts, or should I try it?

BQS4 · 03-20-2003

I think it might be too much carb'ing for a "STOCK" 1.9, but, you didn't say whether yours was stock or not.

RallyBob · 03-20-2003

What size are the chokes? (venturis) This matters more than the throttle plate diameter. I'd say a stock engine can handle them, if the chokes are moderate (30 mm or less) and you jet correctly.

Bob

Jerry C · 03-20-2003

Sorry guys, I didn't give you enough info. First the carbs. Thay are one barrel carbs. They come off a 1000CC 2 cyl. 2 stroke Sea Doo PWC engine. With the carbs jetted as they are now the engine ( rotax ) makes about 130 Hp at 7200RPM and drinks 18 GPH. Now the interesting part. The throttle plate measures 46MM. In the bore is a venturi that is 42MM. Located in the lower third of that venturi is a second venturi for the main jet. It measures about 10MM. There are 3 transfer ports that are adjustable ( fuel and air jets ) main jet adjustable ( fuel and air jets ) adjustable acclerator pumps, adjustable power circuits, Idle circuit is adjustable ( air jet, main jet, and mixture screw )
As far as my engine , I have a stock as a rock 73 GT engine in the car now ( even the solex ) I also have 2 other engnes that i am playing with. I am thinking I should give it a try. What do you guys think? Yep I am nuts.

RallyBob · 03-20-2003

Half the displacement with double the power? Yea, you could say it's a bit too much for a stock late-model smog engine. If you adapt just two of them, that would probably work okay, but the chokes are on the large side. Low end power will not be it's forte. The VE of the Opel is not very high in stock form.

Bob

Jerry C · 03-23-2003

Thanks guys,
I am going to give it a shot. If it works I wil let you know. If not I will let you know too. By the way , I have about 4 sets of these carbs if you want to try to.

commrad · 10-21-2003

man if you get that to work I'll rob the carb off my CR500 for my opel

As a moto X racer/ engine builder just a little to think about those carbs, the idle ciruits and jetting ciruits are not designed for a 4 cycle engine, plus if I'm not mistaken those carbs you have do not have accelerators pumps which would kill your bottom end. All so A 1000 cc 2 cycle theoreticlly pulls in as much if not more than a 2000 cc (2 littler) 4 cycle engine at any give rpm.

just a thought but if you want to use side drafts from a motor cycle or personal water craft get a Dennis Kirk catalog and get 2 Edelbroc "pumpers" designed to work on an XR (4 cycle) you'ld be a lot happier than useing the ones off a 2 banger becuase one thing that designers of 2 banners take to the drawing board is that the engine will all most all ways be kept at over 5000 rpm.

By the way, don't let the Hp out put of the PWC fool you

HP is simple a formula of torque X rpm divided by, arg brain fart
any way point being a little Cox .049 engine makes around 1 hp
but that's only because it turns 20k rpm.

baz · 10-21-2003

huummmmm!!!!!
now what kind of gear box could i put on 300 cox motors ?????????????????????????????????and how would we put a muffler on them?????

do you think the standard clutch will take it

hahaha!

namba209 · 10-21-2003

Commrad, the horsepower formula is P L A N K, divided by 33,000

P = indicated average effective pressure on one piston.
L = Length of stroke in feet
A = Area of a single piston head in inches
N = Number of working strokes per minute, per cylinder, or RPM divided by 2
K = number of cylinders

Also, in one of my other hobbies, I race model boats. I have a number of 2-stroke engines that I run. Here are the sizes and horsepower ratings for them.

.21 cu. in. (3.5 cc) 2 hp @ 30,000 RPM
.45 cu.in. (7.5 cc) 3.5 hp @ 28,000 RPM
.67 cu.in. (11 cc) 4.5 hp @ 26,000 RPM
.90 cu.in. (15 cc) 6.0 hp @ 24,000 RPM

I run 40%- 60% Nitro on these engines, and at $35 a gallon it gets expensive to have fun.

As a joke, I tell folks if I could take out the 15 cu. in. 5 hp engine out of my lawnmower and put the .90 engine in it and have it rotate the blade at speed, I would have a hovercraft.

Thinking along the original thought of this thread, I was considering, at one time, putting the Honda CV 750 carbs on my GT. The biggest drawback to that was lack of an accelerator pump in the carb. Jetting wouldn't be a problem, neither would the mass air flow, because the 750 turns at a much higher RPM than the 1.9. The linkage would be testy to say the least. But it was a thought that I've laid to rest with the advent of the SFI engine I'm putting in the GT now.

Ron

commrad · 10-22-2003

I know Rc engines is way off for this subject but ron would you happen to know where I could get a 7.5 K&B outboard. I have an old one on my Dumas deep V 40 (and I run 60% when I find time about once every 3 years to run it

). Like all my toys includeing Opels I like to keep spare engines laying around just in case. Seems the only toy it forks for though is my opel, I just have walked in the house from doing an engine swap, damn it's hell to pull one oua the top of a gt, even harder to get it back down in there uggggg.

namba209 · 10-22-2003

I just did a Google search and found the K & B website. Check it out, they have just finished a new production run of the 7.5 outboards. www.modelengine.com/kbindex.htm

Also got to namba.com and check out their yellow pages, they've got a whole lot of folks listed that can fix you up with an engine. Off the top of my head is 707 specialties. He is an outboard fanatic and has designed and built lots of stuff for outboards. He's here in CA, but there may be someone closer to you.

IMHO 60% nitro may be too much for a .45 engine, I only run that high in my smaller ones. I've got K & B, OS max, and CMB engines, plus a bunch of spares. I ran in North American Model Boat Association's classes and have "A", "B", "C", and "X" engines. plus a "B" outboard. That go in 10 boats. Depending on the class, in outboards, you can run full out with an expansion chamber exhaust or box stock with only the lower portion of the skeg highly polished.

Now back to Opels, Why in the world are you taking the engine out the top? It is so much easier to pull the engine and tranny out from the bottom with just a cherry picker and a floor jack, and you don't have to split them to do it. Check out my photo gallery and you'll see the 1.9 engine package coming out the bottom and the V-6/T-5 going in the top, because that's the way it works easiest. You still have to disconnect everything the same except the engine/tranny, and it's so much easier to split them when they're outside the car. Just my $.02

Ron

enhale01 · 07-17-2005

Hey willis you said earlier that you had 4 sets 4 of this carbs or an extra for carbs... I am looking to buy a set so I can install them into my 1985 Nissan 720 ST..let me know if you would like to sell a set...contact me delorieryan"at"msn.com... Thanks

Originally Posted by willis

I have a nice pair of 42 MM Mikuni 1V side draft carbs. I am thinking about building 2 intakes and installing them on my gt. Do you guys think this is too much carb for a 1.9 I dont mind if I loose some torque at the lower RPM, but I still want to be able to drive it on the street. Am I nuts, or should I try it?

kwilford · 07-17-2005

Originally Posted by enhale01

Hey willis you said earlier that you had 4 sets 4 of this carbs or an extra for carbs... I am looking to buy a set so I can install them into my 1985 Nissan 720 ST..let me know if you would like to sell a set...contact me delorieryan"at"msn.com... Thanks

I am not sure if you noticed, but this thread is almost 2 1/2 years old...

enhale01 · 07-18-2005

Originally Posted by kwilford

I am not sure if you noticed, but this thread is almost 2 1/2 years old...

Yeah I saw thought it might work....

03-19-2003	#1 (permalink)
Jerry C Opeler Join Date: Jun 2002 Location: Johnston City, IL Posts: 234	Unanswered: 42 MM Mikuni carbs I have a nice pair of 42 MM Mikuni 1V side draft carbs. I am thinking about building 2 intakes and installing them on my gt. Do you guys think this is too much carb for a 1.9 I dont mind if I loose some torque at the lower RPM, but I still want to be able to drive it on the street. Am I nuts, or should I try it?

10-21-2003	#8 (permalink)
baz opel free after 26 years Join Date: Jun 2002 Location: sunderland england Posts: 4,941 Real Name: barry williams Provided Answers: 4	huummmmm!!!!! now what kind of gear box could i put on 300 cox motors ?????????????????????????????????and how would we put a muffler on them?????do you think the standard clutch will take it hahaha!

10-22-2003	#11 (permalink)
namba209 6,000 Post Club Join Date: Aug 2002 Location: Imperial Beach, CA South of San Diego Posts: 6,054 Provided Answers: 6	I just did a Google search and found the K & B website. Check it out, they have just finished a new production run of the 7.5 outboards. www.modelengine.com/kbindex.htm Also got to namba.com and check out their yellow pages, they've got a whole lot of folks listed that can fix you up with an engine. Off the top of my head is 707 specialties. He is an outboard fanatic and has designed and built lots of stuff for outboards. He's here in CA, but there may be someone closer to you. IMHO 60% nitro may be too much for a .45 engine, I only run that high in my smaller ones. I've got K & B, OS max, and CMB engines, plus a bunch of spares. I ran in North American Model Boat Association's classes and have "A", "B", "C", and "X" engines. plus a "B" outboard. That go in 10 boats. Depending on the class, in outboards, you can run full out with an expansion chamber exhaust or box stock with only the lower portion of the skeg highly polished. Now back to Opels, Why in the world are you taking the engine out the top? It is so much easier to pull the engine and tranny out from the bottom with just a cherry picker and a floor jack, and you don't have to split them to do it. Check out my photo gallery and you'll see the 1.9 engine package coming out the bottom and the V-6/T-5 going in the top, because that's the way it works easiest. You still have to disconnect everything the same except the engine/tranny, and it's so much easier to split them when they're outside the car. Just my $.02 Ron Last edited by namba209; 10-22-2003 at 04:23 PM.

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03-20-2003	#2 (permalink)
BQS4 Southern Red Neck Join Date: Mar 2002 Location: Snellville, GA Posts: 6,027 Real Name: Gene Provided Answers: 12	I think it might be too much carb'ing for a "STOCK" 1.9, but, you didn't say whether yours was stock or not.

03-20-2003	#4 (permalink)
Jerry C Opeler Join Date: Jun 2002 Location: Johnston City, IL Posts: 234	Sorry guys, I didn't give you enough info. First the carbs. Thay are one barrel carbs. They come off a 1000CC 2 cyl. 2 stroke Sea Doo PWC engine. With the carbs jetted as they are now the engine ( rotax ) makes about 130 Hp at 7200RPM and drinks 18 GPH. Now the interesting part. The throttle plate measures 46MM. In the bore is a venturi that is 42MM. Located in the lower third of that venturi is a second venturi for the main jet. It measures about 10MM. There are 3 transfer ports that are adjustable ( fuel and air jets ) main jet adjustable ( fuel and air jets ) adjustable acclerator pumps, adjustable power circuits, Idle circuit is adjustable ( air jet, main jet, and mixture screw ) As far as my engine , I have a stock as a rock 73 GT engine in the car now ( even the solex ) I also have 2 other engnes that i am playing with. I am thinking I should give it a try. What do you guys think? Yep I am nuts.

03-23-2003	#6 (permalink)
Jerry C Opeler Join Date: Jun 2002 Location: Johnston City, IL Posts: 234	Thanks guys, I am going to give it a shot. If it works I wil let you know. If not I will let you know too. By the way , I have about 4 sets of these carbs if you want to try to.

10-21-2003	#7 (permalink)
commrad Opeler Join Date: Oct 2003 Location: Toccoa Georgia USA Posts: 7	man if you get that to work I'll rob the carb off my CR500 for my opel As a moto X racer/ engine builder just a little to think about those carbs, the idle ciruits and jetting ciruits are not designed for a 4 cycle engine, plus if I'm not mistaken those carbs you have do not have accelerators pumps which would kill your bottom end. All so A 1000 cc 2 cycle theoreticlly pulls in as much if not more than a 2000 cc (2 littler) 4 cycle engine at any give rpm. just a thought but if you want to use side drafts from a motor cycle or personal water craft get a Dennis Kirk catalog and get 2 Edelbroc "pumpers" designed to work on an XR (4 cycle) you'ld be a lot happier than useing the ones off a 2 banger becuase one thing that designers of 2 banners take to the drawing board is that the engine will all most all ways be kept at over 5000 rpm. By the way, don't let the Hp out put of the PWC fool you HP is simple a formula of torque X rpm divided by, arg brain fart any way point being a little Cox .049 engine makes around 1 hp but that's only because it turns 20k rpm.

10-21-2003	#9 (permalink)
namba209 6,000 Post Club Join Date: Aug 2002 Location: Imperial Beach, CA South of San Diego Posts: 6,054 Provided Answers: 6	Commrad, the horsepower formula is P L A N K, divided by 33,000 P = indicated average effective pressure on one piston. L = Length of stroke in feet A = Area of a single piston head in inches N = Number of working strokes per minute, per cylinder, or RPM divided by 2 K = number of cylinders Also, in one of my other hobbies, I race model boats. I have a number of 2-stroke engines that I run. Here are the sizes and horsepower ratings for them. .21 cu. in. (3.5 cc) 2 hp @ 30,000 RPM .45 cu.in. (7.5 cc) 3.5 hp @ 28,000 RPM .67 cu.in. (11 cc) 4.5 hp @ 26,000 RPM .90 cu.in. (15 cc) 6.0 hp @ 24,000 RPM I run 40%- 60% Nitro on these engines, and at $35 a gallon it gets expensive to have fun. As a joke, I tell folks if I could take out the 15 cu. in. 5 hp engine out of my lawnmower and put the .90 engine in it and have it rotate the blade at speed, I would have a hovercraft. Thinking along the original thought of this thread, I was considering, at one time, putting the Honda CV 750 carbs on my GT. The biggest drawback to that was lack of an accelerator pump in the carb. Jetting wouldn't be a problem, neither would the mass air flow, because the 750 turns at a much higher RPM than the 1.9. The linkage would be testy to say the least. But it was a thought that I've laid to rest with the advent of the SFI engine I'm putting in the GT now. Ron

10-22-2003	#10 (permalink)
commrad Opeler Join Date: Oct 2003 Location: Toccoa Georgia USA Posts: 7	I know Rc engines is way off for this subject but ron would you happen to know where I could get a 7.5 K&B outboard. I have an old one on my Dumas deep V 40 (and I run 60% when I find time about once every 3 years to run it ). Like all my toys includeing Opels I like to keep spare engines laying around just in case. Seems the only toy it forks for though is my opel, I just have walked in the house from doing an engine swap, damn it's hell to pull one oua the top of a gt, even harder to get it back down in there uggggg.

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