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oil pump

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hi all is the standard oil pump on a 58 dommi still able to operate ok if i relocate the oil bag into the bump seat or would you recommend an upgrade 

cheers rob

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Hi Robert,

I don't think your bike is running so it will be difficult to check the condition of the existing pump by oil pressure check, so a quick strip down to visually check the gears and measure the end float may give you some idea.

If it's condition is poor a new pump may be required anyway but simply swapping for a 6 start isn't a simple swap, involving new 6 start worm, new rocker shafts etc.

Hydraulically moving the tank back and up will probably be self compensating as you will have a greater head to overcome the additional distance and the pump suction is quite low and feed relies more on gravity.

I don't know how you will feed the rockers after the change though, needs some extra thought.

Good luck,

Dick

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hi dick thanks for the comment ya need to do a bit more research as i really want to try and move it there is the 6 start worm used in the commander ? 

cheers rob

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Hi Robert,

Be aware that there were several other modifications done at the same time as the 6 start worm drive.

Con rods got oil spray jets, cam followers got bigger chamfers, oil drains were changed, rocker oil feed and spindle type is just for starters. Oil pump gears wider? 

When I built up my 650 'bitsa', I was encouraged by those 'in the know' (and he who knew how to make someone spend money!) to go the plain rocker spindles and pressurised oil feed route because it was essential, but all it ever did was flood the top end with oil so badly that it smoked like a 2 stroke. I would resist the temptation to go that route. In my case, a return to the original set up cured the issue.

What I'm saying is, you are embarking on a lot of modifications, but be aware of unintended consequences.

As to the oil tank in the seat, why not? You won't be the first to do it. The scavenge pump will scarecely notice the difference in height - it is a pump after all. An alternative is the twin compartment fuel tank with the oil tank in there.  More freedom on seat design, shorter oil pipes and again has been done before.

Rocker oil supply? Again, if you stick to the original version I doubt it would make any difference.

Regards, George. 

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The standard oil pump should be OK for this slightly modified routing by Robert. The extra tubing will cause some resistance to the flow of oil to and from the seat tank but using a 20/50W oil will help to overcome this.

The most important factor will be to make sure that the pipe end connections are near perfect. Any badly made connections will allow air into the system and possibly rob the bottom end of oil on start-up.

George has raised an issue that is quite common with owners trying to upgrade their bike's rocker oiling system. Unless the rocker arms have absolute minimal wear, fitting them with plain spindles is just asking for over-oiling in the cylinder head. The scrolled spindles by their very definition are basically drill bit shanks in disguise. They only have half the surface area of the plain spindle and next to no oil supply on engine start-up and often even less when running thanks to the low pressure return feed. Consequently, they carve their way through the rocker arms and leave a large running clearance when plain spindles are fitted.

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many thanks for the comments much appreciated 

 

In reply to by robert_wood

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Don't forget that the tank has to be vented.

Mike

 

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