MS 290 oil pump

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hawkins111

hawkins111

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What is the deal with the extension on the pump shaft? The top shaft came out of the pump housing # 1127 647 0461 A, off an MS290. The bottom shaft is a brand new in the bag Stihl shaft # 1127 647 0600 A. I didn't have time to wait, so I ordered a new pump, complete # 1127 640 3204. The new pumps looks as if it has a shaft with the extension. It also had the same case # 1127 647 0461 A. I did not take it apart to see. What's up here?

Tom
 
I can't tell you the answer, we're going to need a Stihl dealer to sort this one out.

What I am interested in is whether the cam profile that determines the pump stroke are the same. I've got a project saw going and it uses the same pump. I want to increase the pump stroke and I either need to find a different piston rod or modify the existing rod.

Can you tell me if the cam profile (the depth of the ramp on the end) is the same for both rods?
 
MS 290 oiler

Yes, the cams are the same size. The stroke appears to be the same on both. The extension appears to go through the end cap and serves as a support on the end of the shaft. With out the extension the support appears to be on the outside dia. of the cam, which rides inside the pump housing (cast Aluminum).
 
Oil Pump Mod

Terry Syd said:
I can't tell you the answer, we're going to need a Stihl dealer to sort this one out.

What I am interested in is whether the cam profile that determines the pump stroke are the same. I've got a project saw going and it uses the same pump. I want to increase the pump stroke and I either need to find a different piston rod or modify the existing rod.

Can you tell me if the cam profile (the depth of the ramp on the end) is the same for both rods?
Click to expand...

Terry,

Search my thread: Poor Man's Stihl Oil Pump Mod

I have all the spec's and what changes I made. NO COST just a little time.
 
I've got a MS390 torn down in my shop for a pressure test along with the service manual for that series saw. Unfortunately I'm 60 miles away. Tomorrow I'll check back and see if you have an answer yet or not. I am having my own Stihl part issues, I need a fuel line assembly and am impulse hose for a TS400, and it's been ordered for a month....
 
You beauty! (Australian slang for 'good work Mate!') I'll get down to the shop and order the new piston rod.

Ah, do you know the part number for the new rod on the 390?
 
Last edited:
In 2006 they changed the pump to add a bearing bushing that the end piston rides in , so the new piston has the extension on it that is supported by the bearing bushing.
 
So it looks like the new pump piston will fit the old body (and give increased oil flow), its just the bushing won't be on the end of the pump. Looks like I could just cut the end piece off of the new piston rod.
 
Terry Syd said:
So it looks like the new pump piston will fit the old body (and give increased oil flow), its just the bushing won't be on the end of the pump. Looks like I could just cut the end piece off of the new piston rod.
Click to expand...

If you have the old .75 piston then you want the 1127 647 0601 piston which is .88 and will fit in the older housing. I believe you can't put the newer 1127 647 0602 piston in the old housing, only the new style with the bearing bushing.
 
OK, now I've got it. Thanks for the number of the new piston.

The stroke length on the rod I have is only about .4mm - the new piston should put out heaps more oil.
 
Last edited:
Yeah, check out the differences between the two rods. If the only difference is just the bearing surface on the end, you might just cut it off and run it. It won't have the bearing surface but maybe it doesn't need it.

The original didn't need the bearing, so maybe the 'bearing' is to act more like a dust cover for the open cam face. - Hmm, maybe I'll put a rubber plug over mine.
 
Stihl-Pioneer, I went out measured the cam on my pump rod with a callipers and it is only .4mm in movement. Was there an even earlier pump on the 029 that only came with a .4mm piston? The pump body has 1127 cast on it, however there also appears to be another place where 13 is cast on it.
 

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