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Discussion Starter · #1 ·
So, it is finally time to resurrect this project.
20181216_124058.jpg

I had originally intended a CM450E engine for the buggy, but it got donated to a friends project. For posterity's sake, here is the previous build thread:
https://www.hondatwins.net/forums/1...ggy-heart-transplant-cm450e-engine-video.html
Some will note that this was some time ago... ;)
Other projects (and life in general) had gotten in the way, but it is finally in the shop. Taking up pretty much all available space...
20181216_125210.jpg
With the smallish size of the shop, an easy way to maneuver the buggy around was needed so my welder and I came up with this:
20181219_151941.jpg 20181221_154057.jpg
The cart supports the buggy frame leaving me able to work on everything while being able to move it around to get at whatever I need to.
Most of the "to be replaced" bits and bobs have been removed so far and there is a laundry list of "stuff to do"...
I will be cross-posting most of the buggy work on this thread for anyone interested:
https://www.buggynews.com/cb500t-honda-twin-into-a-geo-250-t50143.html

I will post my trials and tribulations regarding the engine and anything else I think of interest here.
A couple things in the works are a hydraulic clutch conversion and a pull start under the dash.
I have some ideas... time will tell how good they are....:cool:
 

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Discussion Starter · #3 ·
Thanks ancientdad, I did see that this summer. It was part of the impetuous to finally get this into the shop... :)

The frame rails that were in my way have been cut out and the engine set in to roughly where it will sit.
20190104_172619.jpg

With the driven gear and chain loosely in place, there will be plenty of clearance.
The shaft will need replacing with a keyed one and I have to acquire some bearings to support it.
20190104_172631.jpg

This is a 15 to 30 toothed set (for a 2:1 reduction) and the FNR has about another 2:1. My back of the napkin math says this should give me good low end pull while reducing my top speed. The rolling diameter of the buggy rear tires is similar to the CB500T and the gears on it were 15 to 33 teeth (2.2:1). Given the CB500T's top speed of ~100mph, I hope to see about 50-55mph in the buggy which will be plenty. The first couple gears will likely be quite short, and starting in second gear might be a thing...
Please, if anyone sees any glaring errors in my assumptions, don't hesitate to speak up.
 

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Am I missing something here? If I read you correctly the buggy rear tires have the same diameter as the 500T.

The 500T with 15/33 gearing (2.2:1) hits 100mph.

Changing to 15/30 gearing (2:1) will increase speed, not reduce it. You're looking at a top end of around 110mph.

I suspect a misunderstanding on tire sizing here.
 

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Discussion Starter · #6 · (Edited)
Thanks to both of you... just the kind of feedback I needed. Made me go through my math a little closer.
Here we go... and again, if anyone sees something wrong in this, please don't hesitate to speak up.

The CB500T came with an 18" rear wheel with a recommended tire size of 3.75x18.
Modern conversion is 110/90-18 or 100/100-18, both have a sidewall height of ~3.89" (times two plus wheel) giving a rolling diameter of ~25.79".
The buggy does indeed have 12" wheels mounted with 24x10-12 tires and has an "as mounted" rolling diameter of ~25.5".

The CB500T has an output reduction of 2.2:1 from the engine to the rear wheel.
The buggy has an output of 2:1 from the engine to the FNR gearbox.
The FNR gearbox has a further reduction of ~1.9:1 (a little tricky to measure accurately) internally.
Combined these provide a total reduction of ~3.8:1 from the engine to the wheels.
This is an increase of 57.8% in reduction from 2.2:1.
Applied to the CB500T's top speed of 100MPH (100MPH / 1.578) gives a new top speed of 63.3MPH.

NOTE: I am unsure if I am applying the increased reduction correctly and there are likely numerous variables unaccounted for.

Given this, I think the buggy should cruise happily at around 50-55MPH.
Also note-worthy is that because of how this is set up through the FNR, the buggy will be able to go in reverse at this speed as well...:eek:
 

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For some reason those tires/wheels on the buggy just don't look that tall in the picture, it could be an illusion. I'm trying to picture an 18" rear wheel and tire and it seems like they aren't as tall as the bike rear wheel/tire would be... but you're there and I'm not, and I assume you've put them side by side to compare
 

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Discussion Starter · #8 ·
I have heard that a picture is worth a thousand words...
20190106_190408.jpg
 

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Well it is, isn't it? I had a hard time thinking of the 12" wheel/tire equating to the 18" wheel with tires, but there it is... so yeah, I guess you're on the right track with the gearing assumptions. that thing should kick up some serious roosts with the torque it'll have. live axle? if so, powerslides are in your future
 

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Discussion Starter · #11 ·
Well it is, isn't it? I had a hard time thinking of the 12" wheel/tire equating to the 18" wheel with tires, but there it is... so yeah, I guess you're on the right track with the gearing assumptions. that thing should kick up some serious roosts with the torque it'll have. live axle? if so, powerslides are in your future
No live axle, it has an independent trailing arm suspension. The differential in the FNR does appear to be locked, but may just be stiff from having sat.

Well now that we have that straightened out I want to copyright the video of that first 55mph ride in reverse!
The front end is light enough that I can pick it up to put jackstands under it, I suspect reversing at speed would range from spooky to downright terrifying.

In any event, I will report here any tom-foolery. Hopefully with videos... gotta convince momma-bear that I need a GoPro...
 
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