premix setup on 200

[rg500g]

I'm trying to help out a fellow who's more or less developing a BS 200 cafe bike for another guy.  It's got some challenges.  The guy who is funding the project has a very strange idea about oil tank placement, and no provision to detect oil level in what looks like a nitrous bottle.  Don't ask...  Over a year ago I tore the engine down totally, cleaned it up and rebuilt it, handed it to him and hope I'd never see it again but here it is, and don't want it ruined because the injector oil is held in a thermos looking thing with the lowest portion even or a bit below the pump intake level.  I'd love to recommend premix for safety's sake, and would appreciate feedback from the list regarding ratio. 

If premix is feasible, and the owner OKs it, I don't want to ruin any parts such as the pump.  Is it OK to leave the pump where it is and not feed it any oil, or must I remove the pump?

[scrambler]

I use pre-mix on my 200 ice racing bike. I run 40:1 Golden Spectro. Old manuals will probably say 25:1 but I think with newer synthetics you can run less.

I removed the oil pump. Not sure if it would cause any problems without running oil through the pump. It might.

[disc_valve]

Hi,

I can't see why the 175/200 engine shouldn't run quite happily on pre-mix.  When the BS90 engine was converted to oil injection, the factory simply bolted on a pump and squirted the oil into the engine via a nozzle just behind the carb stub, with no other mods to the engine internals.

The 175/200 engine uses exactly the same system, relying on crankcase turbulence to distribute oil to the right places. It's effectively a pre-mix system with all the mixing taking place in the inlet tract.

Most of the guys I know who race Bridgestone motors run them on pre-mix these days - whether it's a 90, 175, 200 or 350 motor.

I'd go right ahead and run on pre-mix. Remove the pump but make sure you plug the oil feeds to both sides to prevent it sucking in air and messing up the fuel mixture.

[rg500g]

When the pump is removed you have the worm gear exposed and there's a lot of end play.  The mechanic was concerned about possible oil leak and possibly crankcase leak.  Don't think there's a risk of crankcase leak given location of pump drive, but that worm gear has 3mm or so end play.  The 175 cc diagrams don't show that exposed gear.  Anyone know anything about this?

[disc_valve]

I'm not sure what you mean by the "worm gear". On the 175/200, the pump is driven by a pair of straight cut gears under the oval shaped cover to which the oil pump attaches. The oil pump would be removed as a unit along with the ovel gearcase cover, revealing the small gear pressed into the end of the crank. Are you sure you are talking about a 200 Twin?

If you have a worm gear and shaft exposed when you remove the pump, that sounds to me more like a 90, 100 or 350 engine. This shaft is driven off the the crank via a plastic gear, and the shaft will have some degree of end play. In this case, you will have to remove the transmission case remove the worm gear shaft and refit the transmission case. This will leave an open hole on the transmission case cover which needs to be sealed with a flat plate.

Graham   

[rg500g]

Thank you very much for the post.  I remove the pump and leave the oval cover in place, and there's a shaft with a worm gear that sticks out of the oval cover.  We will remove that oval cover as well.  Hopefully that should do it.

[disc_valve]

 OK, sounds like you solved the immediate problem. On late model 175's (and, presumably, all 200s), the chamber behind that oval cover is splash fed with oil from the gearbox, so if you run the engine without the oval cover you will need to close of that oil feed somehow to stop gearbox oil escaping.  The oil is fed (and returned) through two small holes in the disc valve cover.

It's probably easier to just remove the worm shaft, and then blank off the shaft hole in the oval cover before refittimg it. This method also means you can keep grit and road dirt  away from the crankshaft end seal.

Hope that makes sense -

Graham 

[rg500g]

Makes perfect sense.  We can do this.  Thank you everyone for your assistance on this.

[bsracer]

Maybe like the following

paul

[disc_valve]

Looks good to me!