Engine ideas

Oneaxepony · Apr 4, 2010

For the GX390, what size bolts are used in the universal bolt pattern?

oldmech · Apr 4, 2010

Hi! For most four M8 x 1.25 treads check for length may be 30MM Good Luck! Oldmech

Oneaxepony · Apr 5, 2010

Thanks, oldmech. There are two sets of 4 mounting holes around the crankshaft on the Honda engine. One set of holes are 90 deg apart just behind the circular ring. I believe these are M8 X 1.25. The second set is further away from the ring and only the bottom two holes are 90 deg apart. The upper two holes are 60 deg apart. These bolt holes appear to be larger than M8. These are the ones i'm wondering about. I believe these are the holes Gravelymay uses when he mounts his adapter.

Oneaxepony · Apr 9, 2010

Answered my own question. Found a drawing on-line for a Briggs engine with the universal bolt pattern. Says the bolt holes are 3/8 - 16 UNC. Tried one at home and - voila! - it fits!

gravelymay · Apr 29, 2010

How is your conversion going.

Oneaxepony · May 2, 2010

I am slowly progressing on the conversion of my L8 to a Honda clone. The approach I have chosen is to use the front half of the Gravely crankcase to connect to the tranny and use an adapter plate in place of the rear crankcase half to connect to the new engine. I am using a 1/2" thick aluminum plate to cover the crankcase with a smaller 1 1/4" plate behind it as a spacer (total thickness 1 3/4"). These plates are pretty much done. Need to get final dimensions on drive gear and get it machined. Gear will need to be cut to size, have keyway cut, and be bored to connect to crankshaft via long bolt. Am not ready to post pics yet but will do so later. I've been PMing oldmech & Gravelymay and each has given me excellent advice.

gravelymay · May 2, 2010

Hi One
We need to talk
I have been on another trail.
I am not sure which way you are going ?
So my advice may be wrong??
I though you where going a different way?
Thanks Bruce g

stevem5215 · May 2, 2010

Wow, an engine kit to replace the L8 would be the ticket. I'd consider putting that on. That L8 was good in it's day but the time has come to consider a better engine for it.

Steve

oldmech · May 3, 2010

Hi! GravelyMay is a Master engineer and make very goods jobs You can trust in him.
My system is very cheap. My cost was less $200. Run very well now more 300hrs.
But I think you go to as Belos site. . The shaft adaptor gear can be very expensive and you need a 112mm spacer adaptor between engine and tranny.
Some years ago a NZ Man make a Kit for Honda to Gravely L about $400 as the Belos site . I Write him No more available. Good Luck ! Oldmech

Oneaxepony · May 3, 2010

My approach is not unique but a combination of several already used. I like the idea of using the crankcase as an adapter but I'm only using the front half (WITHOUT THE BRASS BUSHING). The rear crankcase half is replaced by aluminum plates. The gravely drive gear will be cut to length and attached to the clone crankshaft via sleeve & 1/4" key and held together via a long bolt. The sleeve and gear will easily fit through the 2" hole in the front crankcase half. I chose this approach to keep cost down. I purchased aluminum from my local scrap metal dealer and cut it to size using a circular saw. I drilled holes with my cheap drill press. Even though I am not a mechanic I believe I've got the tolerances close enough that it will work. Cutting the drive gear is something I cannot do myself so I am looking for help on that. I mounted the engine on the tranny briefly yesterday (without the drive gear, of course) just to see if the handlebars would clear the muffler and fuel tank. They did. Am still working out how to attach handle bars but I have a few ideas for this. I am in no particular hurry - just taking my time and having some fun. I appreciate all the comments and suggestions given by others on this site. Thanks.