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Oil pump advice required 1974 DT250

09 Oct 2020 17:09
MrBernzo
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Oil pump advice required 1974 DT250 #1
Help required for a DT250a oil pump set up.
This is a long story but I feel I am close to having this old bike back working on the oil injection.
The bike had no pump on it when I brought it. I purchased a pump, throttle cable and worm drive off eBay which ended up being off a 77 model or later. Lesson learnt.
I hunted down a pump off a 74 from a wrecker and had it sent to me. It was missing the cable pulley so I used the pulley of the 77 pump.
Ordered a new throttle cable and installed everything. That's where I am at now.
After a heap of reading and you tubing (dangerous I know) I am trying to get this thing set up right.
Running the bike on pre mix, the pump is turning but pumping very minimal oil. The pump has no stroke at all with the throttle closed. With the pulley fully pressed in, the pump has stroke but moves hardly any oil.
It appears to me that the shaft is not moving full stroke and not maintaining pressure.
I can't set the pump to have 0.2mm clearance between the pulley and the adjuster plate.

Question is, where to go from here?
Being is Australia and shipping times being what they are right now, sending the pump to deet for a rebuild is not appealing.
I have read up and watched instructions on rebuilding the pumps. This is an option. Once again I can buy a kit online but they will take a month or two to ship from the US or UK.
I am considering stripping the pump down and taking the seals to a local supplier then cutting my own gaskets. Has anyone else done this?
Any advice would be appreciated

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09 Oct 2020 17:26
bluntz465
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Oil pump advice required 1974 DT250 #2
Watch

1957 Cushman Eagle 1969 Honda 90 ATC 1969 Honda CB250
1973 Yamaha AT3 1974 Kawasaki KH440 1974 Honda XR75
1975 Suzuki TS75 1975 Kawasaki GreenStreak 90 1975 Suzuki GT550
1975 Suzuki TS250 1976 Suzuki GT550 1976 Indian Chief
1976 Yamaha YZ80 1978 Yamaha IT175 1980 Suzuki GS550
1982 Yamaha IT465J
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09 Oct 2020 20:55
MrBernzo
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Oil pump advice required 1974 DT250 #3

bluntz465 wrote: Watch


Thanks bluntz, I have watched this and used it as my primary guide to set up:)

The problem is that the oil doesn't pump out of the feed line to the cylinder.

The pump is off a bike from a wreckers that has sat in used for God knows how many years. I think it will need reconditioning.

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10 Oct 2020 00:34
Gr8uncleal
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Oil pump advice required 1974 DT250 #4
Might not be your problem, but worth double checking, and that is there is a metal (brass maybe) gauze filter inside the oil tank just where the oil exits. Have a look to see if this is blocked, compressed etc and therefore restricting flow - those little cameras on the end of a wire are great for this.

Also, do you get good flow a) from the oil tank without hose connected and b) from the end of the hose before it connects to the pump?

Finally, if there is a venting pipe on the top of the oil tank, is it clear?
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10 Oct 2020 02:24
RT325
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Oil pump advice required 1974 DT250 #5
If ya getting an oil flow out the bleed screw in the side of the pump then it should pump up to the cylinder at a good rate if you have no plate on the pump so its getting full stroke. I'd pull the fitting at the pump where the cylinder line fits on because there's a tint ball & fine spring in there & it gats fluff & stuff in there but in saying that its more likely to gravity feed into the cylinder rather than no feed under pump pressure. Have a look anyway. Depending on the pump i've seen the ones with a roll pin for the cable roller ramp been forced in too far & stops the pump stroking. It'll drive the pump shaft up but then won't come back due to the roll pin touching it side on. That's pretty unlikely though. I don't see your end pate in the pump pics but its only a reasonably large washer with a 5mm hole & shims or thin small od washers fitted under it to get minimum stroke setting. Basically when the pump is at full stroke with the cable roller right back, then minimum gap is set between the washer & small step on the cable roller. Keep premixing until ya sure. They don't pump a lot if ya winding it by hand & especially at minimum stroke.
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10 Oct 2020 11:33
isetta
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Oil pump advice required 1974 DT250 #6
does anyone know if the cable pulley is the same for the two different bikes. I am wondering the if the cable pulley is adversely affecting it if it is the wrong part. Like the other answer - they don't pump much out when working properly.

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10 Oct 2020 13:54
RT325
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Oil pump advice required 1974 DT250 #7
Never thought of 'that', but couldn't see the pulleys being different enough to 'make a difference'--or not that sort of big difference at least. Good thinking though. Oil pump cables do get rusty & frayed down in the entry to the pump housing through the adjuster 'if it has one', & can hold the pulley open. Funny thing was with farm bikes often the ones that ran the cleanest usually had a broken cable & the pulley had flicked down to minimum delivery. Probably only survived due to the slow running they mostly did following cows home for milking etc. Probably getting 100-1 delivery or something.

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10 Oct 2020 13:54
MrBernzo
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Oil pump advice required 1974 DT250 #8

Gr8uncleal wrote: Might not be your problem, but worth double checking, and that is there is a metal (brass maybe) gauze filter inside the oil tank just where the oil exits. Have a look to see if this is blocked, compressed etc and therefore restricting flow - those little cameras on the end of a wire are great for this.

Also, do you get good flow a) from the oil tank without hose connected and b) from the end of the hose before it connects to the pump?

Finally, if there is a venting pipe on the top of the oil tank, is it clear?


Thanks gr8uncleal. Checked all of these and have good oil flow all the way to pump and through the bleed hole.

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10 Oct 2020 14:00
MrBernzo
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Oil pump advice required 1974 DT250 #9

isetta wrote: does anyone know if the cable pulley is the same for the two different bikes. I am wondering the if the cable pulley is adversely affecting it if it is the wrong part. Like the other answer - they don't pump much out when working
properly.


Great question. Could well be the issue. The pulley is different to pictures I have seen. The pulley I am using does not have the boss for the pin the can stop the cable from coming out of the pulley.

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10 Oct 2020 16:30
bluntz465
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Oil pump advice required 1974 DT250 #10
Check the banjo bolt,before and after. They are not supposed to be reused but we all do. In particular check the oriface in the shoulder that is not deformed or crushed and you can blow through it. Use new crush washers. I think any leak in the system may make pump loose prime.

1957 Cushman Eagle 1969 Honda 90 ATC 1969 Honda CB250
1973 Yamaha AT3 1974 Kawasaki KH440 1974 Honda XR75
1975 Suzuki TS75 1975 Kawasaki GreenStreak 90 1975 Suzuki GT550
1975 Suzuki TS250 1976 Suzuki GT550 1976 Indian Chief
1976 Yamaha YZ80 1978 Yamaha IT175 1980 Suzuki GS550
1982 Yamaha IT465J

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