G1 big block project br250 bravo

[nwarren9]

sir
first thing I broke the engine down gave it a lite hone cylinder ordered rings and order seals and rings just installed them. thanks you

[slonomo]

Originally Posted by nwarren9

slonomo

Yes, thank you. have read it probable 8 to 10 times, I am just having a Ripple things!

working on motor mounting location, needs clearance for carburetor over the rear end. Been trying different wood blocks under motor to get best fit looks like a 1 1/2" lift will work.
Bolt pattern different on Bravo than on the G1 the plan is to take the old motor mount from Bravo rebend each end down 90 deg an trimming off excess steel.

Sounds like you got it then. It always tests our patience and ability when we take on a swap like this, but keep it up, you're doing great! I'll be watching.

[nwarren9]

update I have not had much time to work on project but have some question for the group? I am looking at the possibility of using the 250 bravo sled primer clutch and have some concerns.

primary drive pulley for starter generator. I think if have a tentative answer to this problem by having a pulley purchased at the local farm store and having the center lath larger with the clutch drilled and taped for bolts it may work.

drive belt are the same size meaning wight and bevel not length.

is the bravo clutch compatible with the G1 secondary drive I due know it has a different shifting speeds than a G1 clutch that leads to the last question .

has any one read the book on how to tune a clutch? What due you think of the book ?

Olav Aaen's clutch tuning handbook: Olav Aaen: Amazon.com: Books

Olav Aaen's clutch tuning handbook: Olav Aaen: Amazon.com: Books

Is it a possibility to tune a sled clutch to a G1 engaging speed in real life ?

[slonomo]

Wheeew!

Well just to let you know, I'm doing the very same project but with the Enticer 250 engine. I looked into the Bravo but decided against it for the same reasons you are having trouble, the clutch and starter/gen pulley.

It is possible to retrofit a new pulley to the orig Enticer clutch, however, not sure how well it will work since it was not designed to have one. I mean, anything is possible right? So if you have the parts already and you aren't afraid of ruining them then go for it. I've never found anyone in my searches that did this though. The only problem I see is getting it perfectly centered. If it can be machined to fit perfectly then it should work.

The secondary clutch doesn't know what engine is driving it so yes it will work with whatever engine/clutch combo you use, provided:
1. The belt is the same dimensions for the clutch sheave faces 2. The secondary clutch is in good condition

The only issue I see is the amount of power being delivered to the clutch, and how it is being delivered (at what rpm). The G1 clutch was used on a low rpm, low hp engine and doubling the hp could be a problem, although there have been several people on this forum that did it without problems.

I have not read that book, but I did alot of research of snowmobile clutch tuning, which is what you are talking about. If the Bravo clutch uses fly weights to engage then it can be tuned. Here's the rule of thumb: the heavier the weights, the quicker the engagement; and the lighter the weights the more rpm is needed to get them to engage. It's centrifugal force at work. I've seen some guys tune the G1 clutch (early style) by drilling small holes into the fly weights. This lightened them up and raised the engagement rpm. So the question is....can you add weight to the Bravo clutch weights to make engagement quicker? I don't think you would want to do that if you are using a full stock power Bravo engine. That clutch was tuned for proper takeoff. I'd try it out first and see how it performs.

With all that in mind, I decided to use the Enticer 250 engine because it is almost 100% identical to the G1. The engine cases are identical but the crank is different so you could switch your G1 crank over and use the G1 clutch, belt, secondary, etc, then just tune the primary to match engine output. I purchased just the top end of the Enticer so I will bolt on 1/2 of the package to my G1. Carburator will need to change, but the Bravo carb will fit with a modification to the intake boot setup. Carb linkage/throttle carb/jetting will need to be modified. But that's it.

[yamarancher]

We need pics on this for sure.

[nwarren9]

well the wife has just informed me that this project is on the back burner intill after the first of the year. bummer

[slonomo]

Originally Posted by nwarren9

well the wife has just informed me that this project is on the back burner intill after the first of the year. bummer

"You've given in to the Dark Side.....you know it to be true!"

Sorry for your luck. I'll be looking forward to January!

[nwarren9]

complimenting of spec on G1 and BR250M motors found some very interesting differences between the two motors.
****all information below are approximates and are met for only comparisons only ***

G1 215 cc
9-12 hp approx.
idle speed : 1200 rpm,
engagement of primary drive clutch :1400 rpm
shift to high : 2700 rpm (with governor on) 14 mph
belt size: 1.22"-1.06"x 36.38
Clutch: fixed weights
v belt pulley for starter: yes


Bravo 246 cc
15-18 hp
idle speed : ? rpm,
engagement of primary drive clutch :2800 rpm
shift to high : 3100 rpm ( no governor )
belt size: 1.24"-1.10"x 43.26"
Clutch: adjustable
v belt pulley for starter: none

[smallblock450sl]

Just a couple of thoughts from an old gear head... You know it can be done, just use the best of GMB74's project and some of your own. If you want more engine clearance, how about getting rid of the engine block electric start mounting boss (since you plan on useing the G1 starter generator)? That alone would alow the engine to move forward alot (from the picture, it looks that way). You already have detailed electronic and flywheel info (thanks to GMB74) and his 90 degree trick for the carb airfilter is killer Now the clutch...If the stock G1 clutch will mate with the Bravo crankshaft, I'd use it. You could always "shim" the spring for higher rpm ingagement if needed. Sometimes we over think a build, try to keep it simole, use the parts you have and see what happens. Then maybe your better half won't stop you from playing with your toy.....since no more money out of the family bank account. What ever you decide....Good luck on your build

[nwarren9]

Thank you for the suggestions they are all appreached. Next week project is draw up plans for new motor mounts and to work out clearance problems before fabrication of mount. let you know what I come up with.