Topic: Engine test rig - 750

[jonbuoy]

I'm almost getting to the stage of putting my engine back together, reading up on variuos posts here on oil leaks and the fact that I'm not sure if replacing cam chain and tensioner will be the end of my troubles with engine noise - although primaries look fine.  I am thinking about making a test rig to run my engine up out of the frame. I was thinking of a steel square section frame even my bird poo welds should hold it together, other than rigging up the coils and generator and oil and fuel I don't think it will be too much of a problem to do - I already have the loom off the bike.  Has anybody done this before?  It sounds like a lot of work but I think it might save me time in the long run - my frame will be powder coated too and might save me some scratches.

Any opinions?

Cheers guys. 

[rhinoracer]

It's a good idea, a lot easier to work around the engine but I think it'll take you more time to build than to takethe engine off the frame and reinstall in case you needed too.

[OldSchool_IsCool]

Maybe a scrap frame from a bone yard, but building a mount from scratch seems like a lota work.

[jonbuoy]

Was thinking of something like this

[Jerry Rxman Griffin aka MuthaF'er]

Not sure if something like that would hold it once you fire it up but one advantage you'd have is you'd be able to retorque the head. 

[jonbuoy]

Yeah I think a few tie downs and some concrete blocks might be needed, I don't want it going beserk and chasing me out of the garage    .  Using the electric start will hopefully mean a bit less stress on the frame. 

[Terry in Australia]

I have seen one made by a guy here in Oz, he's made a living from buying and selling CB750's, and is the president of the 750/4 club, so he uses it a lot as a test rig for engines he's either selling, or looking to use.

He made it from a damaged 750 frame, just cutting off the top rails and any other parts that weren't needed, then he welded on some handlebars and dolly wheels so he could move it around his shop. It has a small mower fuel tank permanently mounted on it, and uses a car battery, and is heavy enough that the engine can be started with either the electric or kick starter.

He really put some thought into it, there is a throttle assembly with a "cruise control" so he can lock the throttle at a particular RPM range, (for adjusting the ignition timing, idle mixture and for synching the carbs) a tach, and even a clutch lever for checking the smoothness of the clutch and shift lever operation with the engine running.

It is a great idea, but only if you plan on doing a lot of work with these engines, otherwise just buy one of Gordon's special removable frame rail kits, and then you can do a top-end rebuild with your engine bolted in place, just like the mighty 750's lesser (capacity) siblings! Cheers, Terry.

[Ricky_Racer]

Here's another option...  RR

[Terry in Australia]

Brilliant! Inexpensive to build, and no need to chop up a 750 frame, go Ricky!!! 

[Peterbylt]

It looks like something could be easily fabricated from an old grocery store shopping cart. 

[gerhed]

The only way to drive those little wheels is with a pinch roller.--Check marine supply.

[Bodi]

The car engine stand looks better. You don't have room for the exhaust with the little display stand, and running without any exhaust header is a bad idea.

[Tim2005]

Interesting idea. Don't forget to get yourself a pretty big fan, to keep it cool while you're running it.

[rbmgf7]

when i rebuilt my kz400 engine, i just made one out of 2x4's, wood screws, and wood glue. the whole thing only cost a few bucks and worked just dandy. the engine hung by steel rods through the engine mounts so it could straddle the 2x4 rig (made flipping the engine over easier).  i didn't have access to metal or a welder at the time. albeit, the kz engine weighs half as much so just some extra bracing will be needed for the 750. i had the same idea of running it in the stand so if a problem occured, i didn't have to yank the dang thing back out of the frame.

ray

[jonbuoy]

Thanks, some good points there.  I was hoping just to get up to temp and check for rattles and leaks so hopefully cooling won't be too much of a problem, a house fan maybe if I balance the carbs whilst its out.  I'm going to give it a go anyway, I'll let you guys know how it turns out. 

[Superbiker_uk]

Interesting picture of a Dunstall SOHC engine test rig set up circa 1971/72
Posted for interest. Clearly not something you are going to rig up in your garden shed

The picture of the rig posted by RR looks excellent

[scunny]

that fan would need to be a tad smaller unless you wanted some front tyre love.
the overhead or is that over shoulder pipes could catch on tho 

[Terry in Australia]

that fan would need to be a tad smaller unless you wanted some front tyre love.
the overhead or is that over shoulder pipes could catch on tho 

Just say NO to drugs, Scunny! 

[scunny]

hahaha too late in life to make that decision Terry.
that test bench does have promise as a party piece in the backyard tho.

[jonbuoy]

I Wonder what they used for a load on the Dyno rig there?

[Terry in Australia]

I've seen one in a magazine from the era, the "load" was a big Harley Davidson Disc and Caliper.

[speedracer741]

I built a similar test stand a few years back. It is buried in the shop but I will get some pictures soon. It was constructed of mainly wood but I later added a load brake and air fuel meter for doing jetting. I added some steel bracing in the critical areas and it worked quite well. It has brought triple digit horsepower engines to a stall without disentigrating.......so far

[jonbuoy]

I guess a brake would be as good a load as a dyno - maybe a temp gauge on the disk for power measurement