Dolmar Makita oil pump upgrade/modification.

[jar944]

For anyone still following, The plunger/rotor/spurgear is both the piston and the valve for the pump. The flow control screw actually changes the flow by altering the opening/closing timing of the ports. By changing the location of the pin (turning the adjuster) It shortens the time the intake port is open during the charging portion of the "stroke"

Moving the pin more toward center (as the black adjuster does) reduces the total stroke and displacement of the pump

There is a limit to how much stroke the pump body will allow. Interference with the top screw/spring assembly, (the spur gear hits past a certain point), Too much angle could leave the ports uncovered at the wrong time. The last potential issue is that the steeper the angle the higher the shear load on the adjusting screw pin.

 

[GrassGuerilla]

opcorn: Looking good. Why are the Germans so stingy with oil?

 

[jar944]

So this is basically how it works

And dolmars patent on the piston "seal" (#13)
http://www.google.com/patents/US4465440

DESCRIPTION OF THE DRAWING AND PREFERRED EMBODIMENT

The invention is described in greater detail hereinafter relative to a non-limitative embodiment and the attached drawing which shows a cross-section through an oil pump with a pressure seal.

In the drawing, 10 is a pump casing in which a pump plunger 12 performs a lifting movement. In the case of the embodiment shown in the drawing, the lifting movement is produced by a worm gear 15 and a lifting cam 16.

To prevent a penetration of secondary air during the suction phase from chamber 1 via cylinder faces 12a and 12b into cylinder chamber II, an annular groove 13 is formed in the pump plunger 12 connected via a cross-bore 14 with the oil pressure channel D. The oil suction channel is indicated at S.

 

[jar944]

For some additional info, the modified pump has a displacement of .4cc the stock pump has .28cc.

It still seemed to be light on oil after the first try. I pulled everything down and inspected the parts. The pump was fine but the bar oil channel was partially blocked (noodling likely Didnt help)

Hopefully today it works as expected.

 

[aarolar]

And the kits cost how much?

 

[WKEND LUMBERJAK]

Subscribing

 

[jar944]

It works well enough will empty the oil tank before the fuel runs out when adjusted for max flow.

I cut with a 20" and 32" bar. It was flinging oil with the 20, enough it was dripping off the nose end of the bar. Unfortunately the 32 clogged the bar oil port after a few cuts.

 

[Poleman]

Great job!!!!!! What a boost this would be to us Dolmar fans!!

 

[LogSawyer74]

Any updates on the modified pump? Have you spent any more time cutting with the 32? Very interested to hear how it turned out.

 

[jar944]

Any updates on the modified pump? Have you spent any more time cutting with the 32? Very interested to hear how it turned out.

It works great. Just cut this yesterday. opening up the "lubrijet" oil port solved the cloging for me the pump keeps the chain well oiled @32" you do have to be conscious to the oil level or not fill the gas tank as it will drain the oil tank a while before you run out of fuel

 

[LogSawyer74]

Do you think the plastic adjuster would survive if I increased the angle on the spur gear? Or is the milled adjuster a necessity for this to work?

 

[jar944]

Do you think the plastic adjuster would survive if I increased the angle on the spur gear? Or is the milled adjuster a necessity for this to work?

It may, though the protrusion on the top of the adjuster needs to be taller fot there to be a increase in stroke.

 

[angelo c]

Somebody has to "Sticky" this thread...or contact the Chicoms and have them go to production.

 

[Chris-PA]

Nice work! I don't even have a Dolly but I like to see someone re-design stuff properly and do such nice work.

 

[LogSawyer74]

Very nice work, thanks for posting it!

 

[Poleman]

That AWESOME....In field testing also!!! GREAT JOB and also for keeping us all up to date on this!! This will be a great help who want or need to run longer bars or just increased oiling!! You have addresses the one weakness I
have found on these saws.

 

[fordf150]

thanks to this thread i am trying just the steeper angle on the plunger. I just made it a bit steeper by grinding it on the belt sander. havent used it but it does seem to oil more with just that being done. 32" and this is the first time i have ever seen the chain wet with oil. when i get a chance to actually cut some wood instead of just piss revving it i will give an update.

 

[jar944]

Seeing that the pump rebuild kit is NLA..

 

[fordf150]

that looks serious

 

[jar944]

that looks serious

Lol I was looking the o-ring groove specs.