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Post by barbarossa on Jun 11, 2012 19:57:27 GMT 1
Premix v. oil pump seems to be a regular topic for discussion and I wonder if anyone has ever gone " half-way " by setting the oil pump in the fully open position so the engine is getting maximum oil supply at all engine revs ?
If anyone has ever done this I would love to hear details - how you did it, did you go up one jet size, do the plugs oil up ? etc etc.
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Post by lcrider on Jun 11, 2012 20:09:17 GMT 1
This would not work you would oil up the plugs and it would run like shite .
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Post by rdstars on Jun 11, 2012 20:12:54 GMT 1
That suggestion is up there with Ice'cream deep fried in batter  |
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Post by Deleted on Jun 11, 2012 20:18:07 GMT 1
that sounds nice,
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Post by steve h on Jun 11, 2012 21:29:48 GMT 1
Baked alaska???
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Post by Deleted on Jun 11, 2012 21:38:22 GMT 1
baked alaska is merangue and baked but it is nice
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phil38
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Post by phil38 on Jun 11, 2012 22:14:04 GMT 1
Running premix gives a fixed oil to fuel ratio, the pump tries to do the same thing - more revs means it pumps faster, more throttle means it takes bigger strokes.
Running premix requires bigger main jets to get the same air: fuel ratio, as a few % of the fuel going through the jets is actually oil (so it'll run leaner)
Fixing the pump open would make it deliver more oil than needed, so it'd foul up the plugs, smoke and (as lc rider said) run like shite.
What was the idea behind this?
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Post by 47x on Jun 11, 2012 22:19:49 GMT 1
drugs--------probally!!!! ;D
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Post by steve h on Jun 11, 2012 22:31:05 GMT 1
If you fix the pump at max flow, just use max throtle all the time and use the clutch to control speed. Or fix the pump at half max flow with half throtle (you may have to do this to pacify the neighbours)
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Post by arrow on Jun 12, 2012 6:43:39 GMT 1
Running premix gives a fixed oil to fuel ratio, the pump tries to do the same thing - more revs means it pumps faster, more throttle means it takes bigger strokes. Running premix requires bigger main jets to get the same air: fuel ratio, as a few % of the fuel going through the jets is actually oil (so it'll run leaner) Fixing the pump open would make it deliver more oil than needed, so it'd foul up the plugs, smoke and (as lc rider said) run like shite. What was the idea behind this? Thats not quite true. The pump works by constantly changing the ratio from around 80:1 at idle revs to around 20:1 at full bore. This is what the engine needs, not one set ratio. I recently sent an oil pump pulley to a club member who had the wrong pulley on his pump causing the pump to run at max stroke all the time. At traffic speeds it ran like shite and smoked its nuts off. I always go big on the oil pump shims (who wants to run 80:1 ?  ) if you increase the gap to say 0.4mm the ratio starts off at around 45:1 (much better) and still goes to 20:1 at full bore  The 80:1 ratio is all for emissions and keeping the authorities happy when 2T oil was crap quality. Things move on. The above figures are based on the RD250e, I have not tested the 350 LC to such a degree. I recon the lc motor would shift around 15:1 at full bore setting, and at max revs. |
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Post by marddy on Jun 12, 2012 8:59:42 GMT 1
Arrow,
I have 3 shims on my RD250G Oil Pump. Do you suggest that I remove these three and just add a 0.4 size shim? Yes, I agree with your advice to keep the ratio of 45:1 rather than 80:1 at idle rpm.
Hats off buddy...you seem to have done a PhD on this subject.
When can I hear from you about LC and YPVS?
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Post by marddy on Jun 12, 2012 9:05:21 GMT 1
Running premix gives a fixed oil to fuel ratio, I recently sent an oil pump pulley to a club member who had the wrong pulley on his pump causing the pump to run at max stroke all the time. Is there any way to identify a wrong pulley of an Oil Pump OR how did you do so? |
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Post by steve h on Jun 12, 2012 10:04:24 GMT 1
I never realised the pumps delivery was non linear! Just looked @ a pulley & I can see it, (sharp rise then a level off). I used to commute using premix & it was a real pain, I wont premix again, no need when all this set up information is here. How my fizzy kept going I'll never know, you had to rely on the person with the oil dispenser @ the garage selecting the correct dose( there were regular balls ups & double doses!!) My mate had his school uniform spayed with 2t one morning!!
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Post by Deleted on Jun 12, 2012 12:14:39 GMT 1
i remember that, getting a shot of 2 stroke at the petrol station, in my fizzy oh those were the days
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Post by arrow on Jun 12, 2012 12:38:45 GMT 1
Arrow, I have 3 shims on my RD250G Oil Pump. Do you suggest that I remove these three and just add a 0.4 size shim? Yes, I agree with your advice to keep the ratio of 45:1 rather than 80:1 at idle rpm. Hats off buddy...you seem to have done a PhD on this subject. When can I hear from you about LC and YPVS? Hi Mardy, a 0.4 shim will not give you a 0.4mm gap. The average shim stack I have seen is between 1~1.6mm. You have to measure your gap then measure the shims you have, then do the simple calculation, that is what you need to add or to take away. |
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Post by arrow on Jun 12, 2012 12:43:58 GMT 1
Running premix gives a fixed oil to fuel ratio, I recently sent an oil pump pulley to a club member who had the wrong pulley on his pump causing the pump to run at max stroke all the time. Is there any way to identify a wrong pulley of an Oil Pump OR how did you do so? The pulley in question had the hole for the nipple in totally the wrong place so the cable adjustment marks would never line up. I think it was off an rd200 and the bike was an rd400. The pulley for the lc 250 and 350 is 1m1 or 4L1 both are for 250 and 350. Both interchangable between 250 and 350, pulley's that is, NOT the pumps themselves. The pumps have a different internal gear and are driven by a different pitch worm. |
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Post by arrow on Jun 12, 2012 13:03:36 GMT 1
I never realised the pumps delivery was non linear! Just looked @ a pulley & I can see it, (sharp rise then a level off). I used to commute using premix & it was a real pain, I wont premix again, no need when all this set up information is here. How my fizzy kept going I'll never know, you had to rely on the person with the oil dispenser @ the garage selecting the correct dose( there were regular balls ups & double doses!!) My mate had his school uniform spayed with 2t one morning!! The steps on the pulley correspond to the parts of the carburetors, ie there is a big step up in ratio when the carbs go on to the needles (from off the pilots) then another change in ratio when the main jet kicks in. HTH. |
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Post by bluebellc on Jun 12, 2012 13:24:44 GMT 1
Well I've learned more in the last few minutes than in 36 yrs. using the things!
I was going to pre-mix, now undecided, toss a coin?
We use a lot of small chainsaws etc and have no probs. as long as someone
remembers to put the oil in the fuel!
John
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Post by arrow on Jun 12, 2012 13:29:26 GMT 1
Not as much variation in load or speed in those applications so premix is good.
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Post by steve h on Jun 12, 2012 13:29:59 GMT 1
Arrow your'a fountain of knowledge!! Thanks!
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Post by arrow on Jun 12, 2012 13:31:50 GMT 1
 Cheers
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Post by bluebellc on Jun 12, 2012 13:42:47 GMT 1
Yes arrow you're pointing me in the right direction. Those engines are full-hole most of
the time.
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Post by arrow on Jun 12, 2012 13:47:08 GMT 1
If the system is set up correctly it works extreamly well. You can't run premix ratios of 15:1 on these bikes and expect them to run well when on the city runs. I have heared a TZ750 can run 12:1 full castor too which is dirty, but you don't see many in the carpark at ASDA do you ? |
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phil38
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Post by phil38 on Jun 12, 2012 19:54:51 GMT 1
Cheers Arrow. You have clearly studied this in detail. 😄
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Post by marddy on Jun 13, 2012 5:05:37 GMT 1
Arrow,
Just an after thought...can I use air-cooled RD350 oil pump in a 250LC or a 350LC?
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Post by arrow on Jun 13, 2012 6:44:54 GMT 1
Arrow, Just an after thought...can I use air-cooled RD350 oil pump in a 250LC or a 350LC? The pumps for the twin cylinder motors are virtually all the same, but the pulley's vary and more importantly so does the main gear. It gets complicated enough with just the pumps from the air cooled RD's so I really wouldn't recommend it. Much better to just get the correct pump. |
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Post by midlifecrisisrd on Jun 13, 2012 8:11:55 GMT 1
Never mind running with the pump open.
Strangely I had considered the opposite.
When running premix people talk of seizure on closed throttle, if you left the pump on but without the cable connected and ran pre mix at say 40 - 1 it would supply oil on closed throttle varying with engine speed and make the rest up on open throttle.
Steve
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Post by arrow on Jun 13, 2012 14:14:39 GMT 1
Never mind running with the pump open. Strangely I had considered the opposite. When running premix people talk of seizure on closed throttle, if you left the pump on but without the cable connected and ran pre mix at say 40 - 1 it would supply oil on closed throttle varying with engine speed and make the rest up on open throttle. Steve Now there's a thought. Based on the figures I quoted for the 250e this would give around 27:1 at idle revs and around 32:1 at full bore. |
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Post by midlifecrisisrd on Jun 13, 2012 16:19:24 GMT 1
Never mind running with the pump open. Strangely I had considered the opposite. When running premix people talk of seizure on closed throttle, if you left the pump on but without the cable connected and ran pre mix at say 40 - 1 it would supply oil on closed throttle varying with engine speed and make the rest up on open throttle. Steve Now there's a thought. Based on the figures I quoted for the 250e this would give around 27:1 at idle revs and around 32:1 at full bore. The idea was because of the larger capacity and power increase in mine I wanted some more oil but if I increase the pump setting it is very smokey at low revs. It was also so the premix would stop the very precious tanks from rotting. Very easy to change back and forth also. Steve |
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db8888
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Post by db8888 on Jun 13, 2012 19:18:56 GMT 1
Hi i thought some people would like to see this its the official Yamaha
oil pump tool with all the shims which are stored in the dome at the end of the gauges
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) if you increase the gap to say 0.4mm the ratio starts off at around 45:1 (much better) and still goes to 20:1 at full bore 
Cheers 