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1990 DR350 Oil problems

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So I bought a suzuki dr350 last winter with the intent of getting it running over this summer (and riding it of course). Getting into it I knew it had a problem shifting but after looking online I figured it was just that shift drum bolt that had come loose and was an easy fix so I bought it anyway for $900. Well the shift problems weren't the bolt but instead somehow a previous owner had messed up the shift shaft (the part that came off the shaft and had teeth that mated with the shift drum was twisted and cracked in several places. I have no idea how that was managed without causing damage elsewhere.) and that was causing it to disengage from the shift drum. So this is all fine and dandy get a new shift shaft put the bike back together with a new clutch pack and good to go, but then when it runs it doesn't return oil to the frame sump. I checked the oil pressure and was getting less than 5 psi which according to the manual suggests that the pump has failed or there is a leaking seal or problem with the oil filter. I replaced the oil filter with one from suzuki and the problem persists so I have now taken the engine out and tore it down and with the cases split and oil pump fully exposed I can't for the life of me figure out just what is wronge with it. The drive gear is fine so it isn't missing any teeth looking at both sets of pump rotors they look fine and robust enough that so long as they rotate oil should be moved quite well by them. So I am looking for anyone to give me some advice on where some problem seal areas are in the oil supply lines or some more info on how to tell if the pumps are worn out and will no longer pump effectively. 

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Initially when I first encountered the problem I examined an exploded view and noted that there was supposed to be an o ring on that filter which I did not recall reinstalling. Sure enough I and no o ring there and have since replaced it but the issue of oil not returning remains (I was so hopeful when I had discovered that the ring was missing that it would resolve my problem but alas it was not to be).

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Well i figure that just in case any one happens to be as stupid as me it is my duty to update this thread on just what the problem was. I only figured it out after I had torn the engine completely apart expecting the oil pump to be knackered in some odd way and yet finding nothing unusual in the guts of the beast. So the thing is that this bike in particular leans over too much when it is on the side stand because of damage to the side stand sustained sometime under the care of a previous owner. So without thinking I would let the bike warm up on its side stand then shut it off and check the oil which thanks to the extra lean allowed too mush oil to remain in the crankcase and no oil level to be observed on the dipstick for the oil reservoir in the frame. Also without thinking I performed the oil pressure test with the bike again on its side stand and of course without the oil being able to be sucked up by the scavenge pump intake the pressure registered as too low and I was led to believe that there was an internal oil feed line leak somewhere or the pump was somehow destroyed. 

 

So the morale of the story is that when you do your oil pressure checks always do it with the bike in operating position (namely fully upright) lest your result end up similar to mine and a whole lot of effort being expended removing and dismantling an engine for no reason what so ever.

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Well i figure that just in case any one happens to be as stupid as me it is my duty to update this thread on just what the problem was. I only figured it out after I had torn the engine completely apart expecting the oil pump to be knackered in some odd way and yet finding nothing unusual in the guts of the beast. So the thing is that this bike in particular leans over too much when it is on the side stand because of damage to the side stand sustained sometime under the care of a previous owner. So without thinking I would let the bike warm up on its side stand then shut it off and check the oil which thanks to the extra lean allowed too mush oil to remain in the crankcase and no oil level to be observed on the dipstick for the oil reservoir in the frame. Also without thinking I performed the oil pressure test with the bike again on its side stand and of course without the oil being able to be sucked up by the scavenge pump intake the pressure registered as too low and I was led to believe that there was an internal oil feed line leak somewhere or the pump was somehow destroyed. 

 

So the morale of the story is that when you do your oil pressure checks always do it with the bike in operating position (namely fully upright) lest your result end up similar to mine and a whole lot of effort being expended removing and dismantling an engine for no reason what so ever.

 For others clean the oil pressure check valve and check the spring pressure.

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Could you possibly post pictures or describe where that part is? I can find it on the part schematics but they do not give me any idea where it is in the engine and the shop manual makes no mention of it. 

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