T250 / T350 / GT250 / T500 / GT500 oil pump identification

Everything you want to know about oil but were "afraid to ask"!

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jabcb
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T250 / T350 / GT250 / T500 / GT500 oil pump identification

Post by jabcb »

Bloop2’s oil pump rebuild kit works for the 5 different models.
The pumps also look the same, but they have different flow rates.

I have a spare pump. How can I tell which bike its for?
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

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Vintageman
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Re: T250 / T350 / GT250 / T500 / GT500 oil pump identificati

Post by Vintageman »

jabcb wrote:I have a spare pump. How can I tell which bike its for?
I wondered that myself. I tore down a GT250 and T350 pump for example and the plunger threads and gear look the same. I think I counted revs versus plunger stroke and the same between them but not 100% sure now I didn't spend too much time at it for I had what I wanted and not mixed up.

I think the difference is not the plunges per rev but, the the depth of the plunger stroke controlled by the cam end.

So it's either the cam end of the plunger or maybe even the 10 mm left handed bolt with cam wheel (maybe diameter of wheel matters). Suppose you could take off large bolt with o'ring and measure how far plunger travels at WOT. And, count strokes per revs. Plunger diameter.. never checked that?


I never figured it out. Curious myself
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jabcb
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Re: T250 / T350 / GT250 / T500 / GT500 oil pump identificati

Post by jabcb »

The pump control arm is stamped with a short number. On my T500 its 151.
The part # is 16100-15111.
So it looks like the 151 is the first three digits in the second grouping of the part number.

Suzuki did the same thing with their carbs.
It makes sense because the first grouping basically tells you what kind of part it is.
There is no point to stamping the part with the first grouping because you can see what kind of part it is.

The left-hand-thread priming bolt that’s on the top of the pump is also stamped with a number.
I suspect that these bolts do vary & the number has something to do with the pump flow rate.
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 project & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
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oldjapanesebikes
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Re: T250 / T350 / GT250 / T500 / GT500 oil pump identificati

Post by oldjapanesebikes »

I'm wondering if it has something to do with the oil pump gearing ? For the T500, the drive ratio of pump to engine speed is 1:58.38 (per the service manual). I haven't found the drive ratios for the other models, but it they differed that would allow different pump rates as the pump curves are each quite different even though I think the T250, T305 and T350 all share the same part number for the pump. The T500 pump is a different part number - so perhaps that is due to having a different ramp screw ? 8)
Ian

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jabcb
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Re: T250 / T350 / GT250 / T500 / GT500 oil pump identificati

Post by jabcb »

I checked my two T500 pumps. Both have the control arm # of 151.

The left-hand-thread priming bolts have different #s: 3.9 & 4.0
Checked on eBay & there was a pump listed with 4.1

So its reasonable to assume that the left-hand-thread priming bolts vary & it has something to do with flow rate calibration.

This also suggests that if you have two problematic pumps, you may have problems if you mix & match the parts to make one good pump.
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 project & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
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Alan H
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Re: T250 / T350 / GT250 / T500 / GT500 oil pump identificati

Post by Alan H »

It was more if a technical thing with flow graphs.
Think of how stupid the average person is, then realise that half of them are more stupid than that.
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