Bridgestone Motorcycle Parts Discussion Board

Bridgestone Tech Talk => 350 Talk => Topic started by: husker on August 14, 2017, 09:59:48 AM

Title: Excessive oil consumption
Post by: husker on August 14, 2017, 09:59:48 AM
Took the Gtr out for a ride awhile back and started to miss on one cylinder. When I got to an auto parts store I bought a points file and cleaned up the contacts and that fixed the miss. On the way home the right carb slide stuck in a near wide open position. I stopped to fix that and noticed the 2 stroke oil was below the sight glass. I had topped the tank off before I left. Got some 10w-30 at a gas station to get me home. To have burnt that much oil in 50 miles I would have been setting up a smoke screen behind me but it was not. Drained the transmission and got out 2 quarts which would be close to a pint extra. I use Amsoil synthetic which is not colored any different from regular oil. I took the pump off and removed the worm wheel cover and there is a slow leak out of the worm wheel shaft. Maybe 10cc in 2 weeks. The extra pint could have leaked into the transmission over the last year since it was put back together. I have a spare pump and I could not see any type of seal on that shaft. At even wide open throttle would it even be possible for it to have injected a near tank of oil in 50 miles? What are your thoughts? I am thankful I caught it when I did.  Thanks......................Rod
Title: Re: Excessive oil consumption
Post by: moonpup on August 14, 2017, 02:46:36 PM
This won't solve your oil consumption question/problem, but will give you an idea as to what mileage to expect.....
Title: Re: Excessive oil consumption
Post by: BRT-GTR on August 14, 2017, 05:21:18 PM
                 Can't say where your 2S oil went, leak at rear of tank? Sure you would have noticed that.
         The worm wheel drive behind the oil pump has no seal but has a screw thread cut into to shaft. This pulls a small amount of transmission oil into the oil pump gear box to keep it lubed. Good news is, it's not a leak, it's designed to do that.
    The 2S oil side of the pump is separate from the pump drive and I don't see how it could push oil into the transmission unless there is seal missing. Your pump must have been delivering oil to the cylinders for you to do 50 miles. Something of a mystery?
Title: Re: Excessive oil consumption
Post by: hardy on August 14, 2017, 06:19:13 PM
To verify the flow of oil, you could try running the bike on pre-mix while putting the oil lines to the cylinder into a bucket. If you have excessive oil flow, try resetting your oil pump. There is a thread about it, not sure where it as as not at my computer.

Title: Re: Excessive oil consumption
Post by: husker on August 14, 2017, 07:25:51 PM
Brian the slow drip is seeping out around the plunger shaft and there doesn't seem to be any type of seal on that shaft. But that would not be enough leakage to explain the amount of oil it used. Yes it's a mystery! I was using a lot more throttle when it was running on one cylinder so it was pumping more oil at those times. Maybe Amsoil is smokeless! Should have been raw oil blowing out the muffler. Hardy I will try what you suggest.  Thanks...............Rod
Title: Re: Excessive oil consumption
Post by: BRT-GTR on August 15, 2017, 07:22:14 AM
         Ok, got you now.
       There is no seal on the plunger shaft, it relies on being a close fit in the pump body to stop back flow and for it's pumping action. If you can feel any play don't use the pump.  It's possible someone messed with it in the past. Check the pump stroke as per Graham Weeks article here:- (                   note also the comment about the adjuster back plate coming loose.

    Is the cam pushrod free to move back and forth. These can hold the pump at full open if they are sticky. Whether that would explain the oil usage, I don't know. Manual says full open it can use 600cc (over a pint) at 5000rpm for an hour. So a stuck pushrod might explain the usage. Have you checked the exhausts for the missing oil ? If it did go through the engine, they should be really loaded up.

  You can also check the pump action by introducing an air bubble into the outlet lines. You should then see a small slug of oil pushed alternately to each cylinder.
Title: Re: Excessive oil consumption
Post by: husker on August 25, 2017, 08:25:41 AM
OK I hooked my extra pump up to the line from the tank and bled it out and let it hang there for several days and no oil was dripping out. Timed the distributor and set the volume screw as recommended and installed it on the bike. I am getting air bubbles in the right outlet only to the extent that the oil volume is only half of normal. If the plunger shaft is drawing in air wouldn't both outputs  have air in them?  Another issue I am having is getting the fuel mixture leaned down. I am down to 125 mains, 22.5 pilots, clips in the top grove on the needles, air screws 3 turns out,  fuel level below recommended, and the baffles are clean and its still runs rich in around town riding. It runs good at 60 now but the plugs still are on the dark side. My compression pressure is low (100 and 90lbs) could this be causing the mixture problem? Thanks...........Rod
Title: Re: Excessive oil consumption
Post by: husker on August 25, 2017, 10:01:48 AM
I am puzzled about the assembly instructions for the oil pump. I took a pump apart including the distributor shaft. According to the instructions you put the dot on the distributor gear so it lines up with the center of the plunger shaft. In this position the outlet hole on the distributor shaft lines up with one of the outlet ports on the pump body. Now when you place the plunger shaft  so the back of the worm wheel cam is over the center of the distributor gear (page 44 fig.94 service manual) the slot in the plunger shaft is past the outlet port to the distributor. If you place the plunger shaft in when the cam just comes off the rod the slot is lined up with outlet hole. I hooked the pump inlet to a bottle of oil and turned the wheel by hand and it seems to pump the same amount of oil in either position. Also what is fig. 93 page 44 about?  Thanks.....Rod
Title: Re: Excessive oil consumption
Post by: husker on August 25, 2017, 11:33:28 PM
Found where the air was getting into one of the oil injection output pipes. The banjo fitting was letting air enter. Would have thought there would be a slight pressure in the pipe because of the check valve. Maybe enough crankcase vacuum to pull the air in. Put some silicone gasket around the banjo and it stopped the air bubbles. While working on this today I had both of the pumps I have apart and found out the distributor shafts diameters are slightly different they would not interchange between the pumps. Leaving in the morning with the GTR on a 500 mile weekend trip with some other old bikes. A couple of them also make smoke!......Rod
Title: Re: Excessive oil consumption
Post by: OldSwartout on August 26, 2017, 08:20:39 AM
While working on this today I had both of the pumps I have apart and found out the distributor shafts diameters are slightly different they would not interchange between the pumps.
That's interesting, didn't know that.  They must have done a select fit when the pumps were manufactured to make sure the clearance was exact.
Title: Re: Excessive oil consumption
Post by: BRT-GTR on August 27, 2017, 06:42:00 AM
            I've also been equally confused about Fig 93 in the manual and have never sussed it out.  BS issued a clarification on Service letter BSG-0059 which confirms the correct method of timing the pump gears is as shown in Figs 92 & 94. (        See page 32

      Having recently set the pump stroke myself using Graham Week's method, on reflection, Fig 93 shows the cam position at which you could measure the pump stroke with a dial gauge. Maybe BS were going to include a section on setting the pump stroke but left it out. Graham's method is far easier. There are lots of minor errors in the 350 manual.

      A couple of thoughts on the over fuelling issue.  Are the float pivot pins badly worn on the ends, this is a well known issue and makes it difficult to set the float level.
   Excessive engine vibration can upset the float valve shutoff.   The low compression figure could be causing the problem.

      Let us know how you go on with the road trip
Title: Re: Excessive oil consumption
Post by: husker on August 27, 2017, 11:29:07 PM
Just got home. Had trouble fouling plugs on the way to New Ulm, MN yesterday ran out of plugs and loaded it on the trailer for the rest of the trip. Backed off the oil cable adjustment and bought some B7HS plugs instead of 8's. Didn't have any problem today and averaged about 30mpg. The float pins are tight in the carb body's but the floats are very loose on the pins. I think the low compression is cause poor burning efficiency for fuel and oil. I will recheck the compression tomorrow and refill the oil tank to see how much it used. 800 miles now since the rebuild and I am hoping the new rings in the old chrome bores are still seating in.
Title: Re: Excessive oil consumption
Post by: BRT-GTR on August 28, 2017, 06:48:17 AM
           You were a braver man than me, going on a 500mile road trip with the problems you were reporting, well done.

    The 350s would foul plugs at the best of times, even when they  were new ( with original jettings). Your compression is at the lower limit so I would agree with your poor combustion diagnosis. Floats are a loose fit on the pins, wear at the ends just made it worse.

I'm at the same stage as you, having just got my GTO on the road (legally!) and now sorting out issues, particularly rich running so I'm very interested in your carb settings. I'm also on new pistons in old bores. Compression seems good on the kickstart but I haven't measured it - yet.    I'm surprised by your airscrew setting on 22.5 pilots. I had to almost close the screw before the idle would pick up and decided they were too small in our temperate (cool 8)) climate. Put 25s in , screws now 1.5 turns open which seems about right and she's more tractable at low revs but that may change as I find other issues. Will post separately.

   Keep the feedback coming, good luck, Brian.
Title: Re: Excessive oil consumption
Post by: husker on August 28, 2017, 01:55:50 PM
Not so brave I knew there would be a pickup and trailer following us! Checked the compression and it is still the same at 90 and100psi.  Used 1.6quarts in 370 miles so that's a little high. Brian that service letter mentions the check valves are to prevent engine vacuum from pulling oil from the pump I had best check the valves cause engine vacuum had to have been pulling air into the line the other day. Karl the smaller distributor shaft could be wiggled in the larger pump body. Not really close to a proper fit. I am thinking the manufacturing specs were change at some point.   One guy rode a 1972 CS5 200 twin Yamaha.
Title: Re: Excessive oil consumption
Post by: BRT-GTR on August 28, 2017, 02:21:02 PM
            I've also recently had air being sucked into a pump outlet pipe due to a loose union. Graham Weeks  reported the same from a split pipe. Don't worry about it, it's something they just do.    Your check valves are probably OK.           Don't take them out unless you have to or you have had them out recently.  The threaded part is very weak and will readily shear costing you a new set. :'( but at least you get to  see how they work  ;)
       I'm not even sure the engine can suck oil from the pump on the 350 due to the addition of the distributor valve.      Oil can flow through the pump on a 175, however.   
Title: Re: Excessive oil consumption
Post by: husker on August 28, 2017, 03:07:15 PM
 Thanks Brian that's good to know.
Title: Re: Excessive oil consumption
Post by: BRT-GTR on September 13, 2017, 09:59:06 AM
    Having got my GTO on the road a few weeks ago I can report that I am also getting 2S oil being pushed back into the crankcase by the oil pump., so yes it can happen.
 The likely source is leakage back along the pump plunger shaft. After about 30 miles running, the pump gearbox was full of red 2s oil and the main case oil has a red tinge.

     Have put a better pump on with new seals and will see now it goes. I'm using fully synthetic, high performance 2S oil which is quite thin and 'searching' so I wonder if this is part of the problem ? Also, the back end of the plunger shaft is a very loose fit in the bearing? at the pump cover end where the spring is housed. Checked 3 pumps and they are all the same,  were they designed like this ?.  If so, this means all the side thrust on the plunger shaft from the worm gear is taken on the thin main shaft of the pump, which is not good.

    Regarding leakage from the inlet/outlet unions, try putting an extra washer on the unions( or all new ally washers). The banjo bolts are very close to bottoming out on their threads after they have been tightened a few times and are unable to pull up properly.

     We can't be the only owners who have had this oil backflow problem, what are others doing ?                                              Brian.
Title: Re: Excessive oil consumption
Post by: AlanJohn on September 14, 2017, 11:46:19 AM
I use belray fully synthetic from Averys motorcycles recommend by Richard Clarke not the cheapest but l belive worth it