Modded Yamaha

[proprider01us]

40hp Modded Yamaha had it's first "fire in the hole" this morning. Going to time it, break it in then see if it can run with the big dogs.

[kampenracing]

I have one of those too. There are two that run in NBRA. I have one and Dick Falbe has the other. We run expansion chambers on both of ours. They run very well. I tried to run mine on my Hemp DMH and it wasn't enough boat!!!!

[Mark75H]

It will be interesting to see how a different motor runs in 850.

Keep us up to date on how it goes

[Tim Kurcz]

40hp Modded Yamaha had it's first "fire in the hole" this morning. Going to time it, break it in then see if it can run with the big dogs.

Looks very nice Joe, you've been busy!

Tim

[1100r]

That is a nice looking motor!! Already looks fast. Keep us posted on how it runs would like to know the results
Todd

[proprider01us]

Thanks guys, hope to get some testing in at the end of May. If all goes well, plan is to start racing it in June. I will keep you posted with results and videos.
Joe

[proprider01us]

The modded 40hp Yamaha has been on the back burner for a few months. I had the head/water jacket machined to fit the cylinder head temp. gauge. Have the carbs jetted @ #130 and the timing set @ 28 degree. Plan to test it in a couple of weeks at the boat races.

Anyone have an ideal head temperature I should be aiming for? I hope to get an exhaust temp. reading eventually when I get the proper probe. Can't wait to see what this little looper will do on my gps!

Joe 2-H

[Ballistic]

Nice. What kinda carbs are those?

Can u tell me something more about the timing? how to you measure and adjust it?

[proprider01us]

The carbs are from a Yamaha 50hp. The timing is fixed, while in operation. Since I primarily run @ W.O.T., I set the timing up for maximum setting. I adjust it, when I need to, with a timing light.

[Ballistic]

Thats funny, My 50 carbs look way different (bigger)

I was wondering on how to adjust the timing. I am giving my 40hp some mods too and i want to advance timing but i have no idea how.
Could u give a short explenation? it would really help me out.

Again, your mower looks awesome :)

[proprider01us]

Yamaha 40hp.

http://youtu.be/uqRzw5Tihu8

[Ballistic]

Looking nice bud.

Why no 70hp carbs?

[proprider01us]

I recently got a set of 70hp carbs, just haven't got them together yet. Those, and a spacer plate for the exhaust, are next.

[biggdave92]

question: how do you get the ring off the flywheel? i have a 25/30 3 cyl yamaha i'm playing with. looks to be pressed on the same way as the 40. love the pics and video!

[proprider01us]

Yes, the flywheel is pressed on. Reduced a lot of rotating mass gettin it off there.

[Karl Kretzmann]

Make sure that its the "square" type carbs! they much better than the " round " bowl carbs!

love what you've done with the yamaha!
i specialize in modifying Yamaha 50's and did something similar in early 2000's. will try to find some pics and post them!

what speeds are you running? what RPM?

what compression?
what internal mods?

[Ballistic]

Make sure that its the "square" type carbs! they much better than the " round " bowl carbs!

love what you've done with the yamaha!
i specialize in modifying Yamaha 50's and did something similar in early 2000's. will try to find some pics and post them!

what speeds are you running? what RPM?

what compression?
what internal mods?

Disagree, The round bowl ones run harder here... They burn the fuel harder too :)

[byrdsperformance@tds.net]

Why do you say square bowl 70 carb's ????:confused:

[byrdsperformance@tds.net]

why do you say square bowl 70 carb's ????:confused:

are BETTER

[Karl Kretzmann]

I found better airflow through the "square" carbs.
Also, depending on level of porting, I ran 90 carbs. Biggest limiting factor I found on the 50's were the reeds! I ended up modding the intake and fitted 6 petal reed block instead of the stock 4 petal! Made HUGE difference! Bare in mind there were many more mods required!!

[calvin]

Great lookin run..WOW..83 is movin!!

What boat do you have it on?

[proprider01us]

The boat that I run the Yamaha on, is a hydro that I built myself. The hull was built for the 44ci Mercury @ 12ft, but it handles the lightweight Yamaha well.

[proprider01us]

Karl,
So far I've only got it going to 83mph testing. The reps at that run was 7800rpm. The cylinder compression is 175psi and I only run VP Race fuel with 16/1 oil.


Make sure that its the "square" type carbs! they much better than the " round " bowl carbs!

love what you've done with the yamaha!
i specialize in modifying Yamaha 50's and did something similar in early 2000's. will try to find some pics and post them!

what speeds are you running? what RPM?

what compression?
what internal mods?

[proprider01us]

Karl,
Can you explain to me the specific advantage to the "square bowl" carbs over the "round bowl" ones. I was told that, of the 70hp carbs, the round bowl ones were the only ones that would fit within the tight cluster of 3 on the intake.

According to class rules, I have to run the 4 petal reed cages. It's quite obvious that this is currently a BIG choke to the intake flow. Did you do any modifications to your reeds/cages in your earlier modified motors?

The internal mods on my 40hp were basic. Crank was welded, head was tightened and all the block work was performed by, none other.............Tim Kurcz!

Did you find the photos of your modded Yamaha's yet. If you don't want to post them, can you P.M. them to me.

Thanks,
Joe:cool:


Make sure that its the "square" type carbs! they much better than the " round " bowl carbs!

love what you've done with the yamaha!
i specialize in modifying Yamaha 50's and did something similar in early 2000's. will try to find some pics and post them!

what speeds are you running? what RPM?

what compression?
what internal mods?

[Karl Kretzmann]

Hi Joe,
you running the old "D" Model block by the looks of things.the newer H model IMO is the better motor, however this is a hotly debated topic!
the 70 and 90 square carbs bolt right onto the H model motor. I'm sure with minor mods you could get them to work on yours.
Th e square carbs definitely "measure" fuel better and are much more responsive. airflow and venturi velocity is much better.

If you cannot change reeds, then you can definitely modify them(if allowed). we ran Bouysen reeds and left only a seat area of 1mm. This means that there is quite a bit of material you can remove. angles and flow are critical! but this is hard to explain without drawings or pictures. just picture airflow through reed block and make it as straight and smooth as possible!

try to find out what was done on the porting?

how much was taken off the head?
any squish angle mods?

haven't had chance to look for pics of my motor yet. will try asap.

Karl


Karl,
Can you explain to me the specific advantage to the "square bowl" carbs over the "round bowl" ones. I was told that, of the 70hp carbs, the round bowl ones were the only ones that would fit within the tight cluster of 3 on the intake.

According to class rules, I have to run the 4 petal reed cages. It's quite obvious that this is currently a BIG choke to the intake flow. Did you do any modifications to your reeds/cages in your earlier modified motors?

The internal mods on my 40hp were basic. Crank was welded, head was tightened and all the block work was performed by, none other.............Tim Kurcz!

Did you find the photos of your modded Yamaha's yet. If you don't want to post them, can you P.M. them to me.

Thanks,
Joe:cool:

[Art Kampen]

Karl,
Can you explain to me the specific advantage to the "square bowl" carbs over the "round bowl" ones. I was told that, of the 70hp carbs, the round bowl ones were the only ones that would fit within the tight cluster of 3 on the intake.

According to class rules, I have to run the 4 petal reed cages. It's quite obvious that this is currently a BIG choke to the intake flow. Did you do any modifications to your reeds/cages in your earlier modified motors?

The internal mods on my 40hp were basic. Crank was welded, head was tightened and all the block work was performed by, none other.............Tim Kurcz!

Did you find the photos of your modded Yamaha's yet. If you don't want to post them, can you P.M. them to me.

Thanks,
Joe:cool:
Joe I don`t know if you have done any mods on the exh side but there is a lot to be gained there than any other part of the engine in my opinion ovaling the port and making it wider & raising the port approx. 3/16 to a 1/4 in.and installing a expansion chambers did more for our engine than any other thing we did. I would suggest also that you go to a aftermarket ignition either from MSD or ELECTROMOTIVE, We have MSD on our engine that was sold as a kit for 3 cyl SeaDoo. Fly wheel that we have on their now weighs approx 1 Lb. If I were do it over I would have used An Electromotive system simply because their Tech assistance is much more friendly and helpful. I wish we had more time to run thiengine. But our priorties now are D- E hyd & run in NBRA 4 classes in a day are more than this old man and my son can handle. Art K

[88workcar]

The outside of the square bowl carbs are much larger, hard to fit. I found that on my 90 the square bowl carbs measure 100 thousands less between the bolting flange and the dump tube. I did see better acceleration, but nothing else. Not one more rpm. Do you want me to find a set of squares for you? Just keep in mind that the 70s allow more airflow weather round or square.

[Ballistic]

Th e square carbs definitely "measure" fuel better and are much more responsive. airflow and venturi velocity is much better.

Thats funny, I experienced a way more "alive" motor with the round carbs.

Depends on other mods i guess which is best.

[proprider01us]

I'll just stick with the round carbs, for now. Until I can open up the "choke" between the carbs and the crankcase, I don't think the inlet flow is going to help that much.

[Karl Kretzmann]

That's pretty spot on!!
The whole carb issue only really come into play on highly modded motors!!
The reeds limit any larger carbs effectiveness!

Exhaust port mods alone could give you extra rpm but if you want complete power mid and top end then it become a complete mod motor package! Ie: carbs,reeds,ports, heads, exhaust, plus plus plus...




I'll just stick with the round carbs, for now. Until I can open up the "choke" between the carbs and the crankcase, I don't think the inlet flow is going to help that much.

[Ballistic]

I found better airflow through the "square" carbs.
Also, depending on level of porting, I ran 90 carbs. Biggest limiting factor I found on the 50's were the reeds! I ended up modding the intake and fitted 6 petal reed block instead of the stock 4 petal! Made HUGE difference! Bare in mind there were many more mods required!!

Hi Karl,

Dit you get this 6 petal reed cage off a different motor or did you create it yourself?

Wouldnt making a 2 petal reed cage be more efficient?

[byrdsperformance@tds.net]

Hi' Joe
A 70 front can be fitted to a 40 .
If you decide to enlarge 40 cage's be carefull.
To much matiral removed an reed collapse can happen:

[OUTBOARDER]

I found better airflow through the "square" carbs.
Also, depending on level of porting, I ran 90 carbs. Biggest limiting factor I found on the 50's were the reeds! I ended up modding the intake and fitted 6 petal reed block instead of the stock 4 petal! Made HUGE difference! Bare in mind there were many more mods required!!

Was going to prep a Yamaha or Tohatsu 42.6 but rules were restrictive at the time.
HAVE THE RULES FOR THE YAMAHA 42 TRIP CHANGED ?

After going thru a Yami and Tohatsu 42 to measure stuff it became apparent that
the intake system as a whole was the bottle neck to competing with a larger engine.Compared to a 49.7 omc intake system it's not even close.

That engine in the video sounds like it is dialed in on the money! Especially when you squeeze it. Bet it turns a lot bigger prop, Big question is how much punch will you have to give up to swing a 90mph wheel????

[Karl Kretzmann]

Hi Karl,

Dit you get this 6 petal reed cage off a different motor or did you create it yourself?

Wouldnt making a 2 petal reed cage be more efficient?



Hi Ballistic,

2 petal would be more efficient if you could find one much bigger than stock. for me it was easier to take the reed blocks off the from end of an 85 or 90 Yam, and weld it onto the case of the 50. I cut off the whole lot, carbs and all!
the best i could get out of the std 2 petal with max mods was around 85 BMEP. stock 85 intake gave me 125 BMEP ( going on memory here so don't take exact figures as fact)
this basically means that with the 3 petal reeds and larger intake..... you could go crazy wild on the porting!

[Karl Kretzmann]

Hi' Joe
A 70 front can be fitted to a 40 .
If you decide to enlarge 40 cage's be carefull.
To much matiral removed an reed collapse can happen:


removing material from the reed seat is a risky one. many failed attempts to find the limit!
also many sets of reeds!.... rather expensive!

[Ballistic]

Hi Ballistic,

2 petal would be more efficient if you could find one much bigger than stock. for me it was easier to take the reed blocks off the from end of an 85 or 90 Yam, and weld it onto the case of the 50. I cut off the whole lot, carbs and all!
the best i could get out of the std 2 petal with max mods was around 85 BMEP. stock 85 intake gave me 125 BMEP ( going on memory here so don't take exact figures as fact)
this basically means that with the 3 petal reeds and larger intake..... you could go crazy wild on the porting!

Thanks for the info.

But i mean a 2 petal reedcage in total. just 2 big reeds. One on the left and one on the right.Wouldnt that be more effecient?

Which parts do you take from a 85/90? The plate the carbs bolt on to? the reed cages? Or something else because i don't see how you can put any bigger reedcages in the 50 block. Its rather small. I over-bent the reedstops a bit and i almost couldnt get the reedcage back into the motor.

[byrdsperformance@tds.net]

If you are still use stock reed's they must go.
A broken steel reed can wipe your nice engine out.
You will find different type's of composite reed's.
Single, dual , carbon or glass ect. An many various opinion's
With a wide single or dual type reed you can remove center diveder's,
an some more from the stock cage's Some even cut out side's an,
mount a reed,s ? As far as a 3 peddle front all the 40 runner's, cage's,
mount flange an ove course reed to carb adpator plate are replaced,
Machine 40 frt. runner's off weld 3v runner's on .:cool:

[Karl Kretzmann]

Thanks for the info.

But i mean a 2 petal reedcage in total. just 2 big reeds. One on the left and one on the right.Wouldnt that be more effecient?

Which parts do you take from a 85/90? The plate the carbs bolt on to? the reed cages? Or something else because i don't see how you can put any bigger reedcages in the 50 block. Its rather small. I over-bent the reedstops a bit and i almost couldnt get the reedcage back into the motor.

If you could find a reed cage with no resistance to flow... that would be best! but that doesn't exist!

i chopped the reed block off the 50 case, and welded on the 85hp's! then used all the 85 hp's plates, reeds, carbs etc.

[Ballistic]

This is what i mean:
http://www.thunderproducts.com/Banshee%20reed.htm

I think im gonna give this a go because i am currently running a 50horse with 70 carbs and i think the reedcages are a big restriction.

[byrdsperformance@tds.net]

Ballisic,
This is quite simular to cage mod's i do.
As the center's are removed i leave apx. 1/8" of runner at top of cage's.

To help guard against reed collapse.:eek:

[nitrohead13]

can the 50hp carb fit 30hp?
can help me with my 30hp?

[quty06]

This is what i mean:
http://www.thunderproducts.com/Banshee%20reed.htm

I think im gonna give this a go because i am currently running a 50horse with 70 carbs and i think the reedcages are a big restriction.

good idea... but where i can get one ( the reed ) or i can use the banshee reeds on my 50 cages?

[quty06]

can the 50hp carb fit 30hp?
can help me with my 30hp?

u need custom made adapter for it

[Lil' Blue Rude]

good idea... but where i can get one ( the reed ) or i can use the banshee reeds on my 50 cages?

If anyone can make a custom reed for it Chris Carson can. Get in touch with him and he should be able to hook you up with a custom reed of some kind.

[nitrohead13]

how about the tunning is it hard?isnt it to big for 30hp or the perfect size?

[nitrohead13]

can he make for 30hp?

[CanadaScott]

Those hose going to the middle leg to the tuner area... For cooling?

[proprider01us]

Yes, there pumbed into the bottom water intake to the block. Have all cooling venting on the tuner and out the top of the block.