why not mount a 4 stroke in the frame?

Kraash

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Jul 29, 2008
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i have no idea what is a better engine (4 or 2) but it seems only 2;s are put in the frame .. why is that? i dont care for the rear mount style.
 

jasonh

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Jun 23, 2008
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Longmont, CO
The 4-strokes are a bit larger. There are a couple kits out there for mounting 4-strokes, but they're hard to come by it seems.
 

BillyB

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Jul 21, 2008
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Los Angeles
I'm waiting on one that's back ordered, but it seems that you have to modify the cranks in order for the pedals to clear the sides of the engine.
 

BillyB

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Jul 21, 2008
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Los Angeles
4 stroke in the frame? Hmmm seems like I've seen one of those....where was it....oh yeah! It's in my garage!
So how did you widen the cranks?

I see something in the picture of the Grubee kit that looks like it would be a one piece crank.

Are there any other viable options?
 

jasonh

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Jun 23, 2008
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Put the crank arms in a vice, heat em up with a torch and bend them. Seems like that would be the simplest way to deal with it if the kit parts won't work.
 

HoughMade

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Apr 15, 2008
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I have the Grubee 1 piece widened crank and I used it at first, but then I switched to a short crank from a 16" kids bike. It does not rise high enough to interfere with the engine mount.

[edit]

Actually, it is more accurate to say it clears the mount on both sides (by about 1/4" on bother sides, but is not long enough to hit the engine shroud or gearbox.
 

BillyB

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Jul 21, 2008
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I have the Grubee 1 piece widened crank and I used it at first, but then I switched to a short crank from a 16" kids bike. It does not rise high enough to interfere with the engine mount.

[edit]

Actually, it is more accurate to say it clears the mount on both sides (by about 1/4" on bother sides, but is not long enough to hit the engine shroud or gearbox.
Does anyone sell cranks that will fit onto a modern bottom bracket?

I'm really not too keen on one piece cranks, and I'm not even sure I can find a conversion kit for my Mountain Bike.

Edit: Does the kit come with the complete bottom bracket parts, or just the wide one piece crank?
 
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HoughMade

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Apr 15, 2008
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Valparaiso, IN
This kit is out of stock about everywhere right now, but it cane with bearings and races that were, I believe, designed to allow the one piece crank to be used with bottom brackets made for a 3 piece. I did not use them be cause I started with a 1 speed cruiser frame. I have seen widened crank arms for a 3 piece out there- but not with the Grubee kit. My legs brush against the gearbox, but with pedal extenders they would not.

However, I have designed my bike to be very individual- look at that pic above for a second and tell me whether I pedal much. I only use the pedals to start from a dead stop so I run cranks under 5 inches with a 36 tooth front and a 10 tooth rear....not going to pedal up to a very fast speed with that setup- but leaving from a stop is downright easy.
 

shiloh0

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Jun 28, 2008
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on my 4 stroker, the kit came with the wider crank arms, but i had to buy the old-style (cup and bearings) adapter. the sealed, newer better quality adapter turns out to be too narrow. this is info for anyone who already has a 3 piece bottom bracket but still runs into problems with crank arm clearing the motor.
 

Dan

Staff
Staff member
May 25, 2008
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Hough, dunno how long I have been admiring your bike and never noticed it had short cranks. Very cleaver!
 
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spad4me

New Member
Jan 20, 2008
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Arizona Bullhead
HiughMade I have admired your bicycle for a while.
I was not willing to use the crank sets offered by the kit makers.
Your solution is elegant.
QUOTE
I have the Grubee 1 piece widened crank and I used it at first, but then I switched to a short crank from a 16" kids bike. It does not rise high enough to interfere with the engine mount.

[edit]

Actually, it is more accurate to say it clears the mount on both sides (by about 1/4" on bother sides, but is not long enough to hit the engine shroud or gearbox.
.
I want a honda, with a cvt, with a frame mount, on a good bicycle.

LOL three inch diameter pedal movement. Almost like pegs.
 
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happyvalley

New Member
Jul 24, 2008
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upper Pioneer Valley
i have no idea what is a better engine (4 or 2) but it seems only 2;s are put in the frame .. why is that? i dont care for the rear mount style.
To each their own, of course but the answer to that question is the reason I won't mount an engine in the frame.
It is upmost for me that bikes retain 100% of their pre-motorized utility and the component group on my bikes is far too important to ever think about replacing a quality crankset with some one piece affair.
 

tyrslider

New Member
Sep 26, 2008
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RainCity
There are solutions for virtually every cycle and bottom bracket set up. I have 3 piece on my mtb that utilize the original bb but w/ only 1 fr sprocket. I understand HV what you are saying about the componantry but can't stand the idea of putting more weight directly over the rear wheel; if I do a rack job it's goin' on the front. But the best place (physics wise) to distribute the weight is in the frame, low and center.
 

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Dan

Staff
Staff member
May 25, 2008
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Moosylvania
Been thinking about this a lot. I love the challenge of working in the parameters of a conventual bike. Frame, front or rack, you have to get it to work. Be easy to just in frame mount and lose the peddles, build a fork or throw a rack on the back... But then we have to reduce the RPMS, vibration and make it pretty. This is functional art. All in the eye of the beholder true, but this art has to work, function and move! There is no right, wrong or left. There is your art. And she is pretty!

My next build is to be a rack mounted ugly as sin work bike that is to tow a small boat. One after that will fly!

Build some thing cool!
 
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happyvalley

New Member
Jul 24, 2008
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upper Pioneer Valley
There are solutions for virtually every cycle and bottom bracket set up. I have 3 piece on my mtb that utilize the original bb but w/ only 1 fr sprocket. I understand HV what you are saying about the componantry but can't stand the idea of putting more weight directly over the rear wheel; if I do a rack job it's goin' on the front. But the best place (physics wise) to distribute the weight is in the frame, low and center.
Cool, I must admit that's a clean looking install, high and tight. So you were able to keep tread distance the same as original then?

Weight is not really an issue for me as I've pretty much focused on Robin engines, 7 lbs. and trying to keep the drive around the same, total setup around 14. Been working on some rear engine placements low and close to the seat post also.

But you know how it is.....or can be, spending a lot (too much) time and money building up frames, scrounging up decent component groups. My goals are always to keep things in line with MAB, motor assisted bicycle, and the engine has to be low impact on the bike and keep it as originally functional
as possible.
 

MotorbikeMike

Dealer
Dec 29, 2007
477
1
18
Sacramento
Hi Guys, I like the 4-stroke in the frame, I just did not like the Chinese gravel-grinder transmixers they came with! Call me old-fashioned, buy the only whining and growling I am used to comes from INSIDE the house, NOT out on a ride!

BUT, I have been exposed to a rumor, that EZ Motorbike will soon be releasing some phase 1 kits, and thiers is guarenteed to be quiet and smooth.

At this time, it would seem that you could install an in-frame 4-stroke, and have a smooth Silent-Power transmission, with the little 4-stroke, snuggled down in the frame, right where it belongs!

I am excited to see one myself, and surely will be ordering one so that I'l be able to see for myself!

I like both quiet and noisy exhaust on 4-stroke, and now if the muffler is quiet, I will not have to listen to what sounds like a tin-can full of howling cats!

I'm excited! this guy did not bring it .santa, tho maybe the New Year guy will?
Mike