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Author Topic: High oil consumption on 500 classic  (Read 243 times)

ajb235

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High oil consumption on 500 classic
« on: April 02, 2014, 05:17:10 AM »
I rebuilt my 94 500 classic last year, new roller bearing crank, new (standard compression) piston, alloy barrel, new valve guides, new exhaust valve, and recut the valve seats to 3 angle type. Also added stronger valve springs.
After only around 1500 miles, oil consumption is high, I used all the oil from high mark to below the low mark in the oil tank.
I attach some pics of the cylinder head and valves,and the top of the piston showing the carbon build up. The exhaust valve seat and valve are pitted, once I got all the carbon off.
I am now reassembling with valve guide oil seals, I need to get back on the road for various events, but would appreciate any comments and advice re improving oil consumption.
The piston has some slight damage to the top land(see photo). Would this cause the problem

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Thanks
Ajb235

Mr.Mazza

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Re: High oil consumption on 500 classic
« Reply #1 on: April 02, 2014, 05:29:08 AM »
Could it be wet sumping on start up? Smoke from exhaust? Running the right grade of oil? Too thick/thin could cause oil starvation? Bad fuel could cause carbon build up. Maybe the rings didn't bed in properly, how did you break it in?

Just some ideas.
Lizzy - 07 500 Deluxe ES - Red and chrome

ajb235

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Re: High oil consumption on 500 classic
« Reply #2 on: April 02, 2014, 05:31:01 AM »
Sorry, I should have said that the oil consumption on the last trip ,250 miles, took almost the whole  capacity of the tank. Its 1500 miles since the rebuild,I have to top up after every run  and its getting worse! 
Will try again to upload photos.

Ajb235

ace.cafe

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Re: High oil consumption on 500 classic
« Reply #3 on: April 02, 2014, 07:04:38 AM »
What piston to cylinder wall clearance did you use?
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High On Octane

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Re: High oil consumption on 500 classic
« Reply #4 on: April 02, 2014, 07:16:35 AM »
What piston to cylinder wall clearance did you use?

+1

Did you properly run in the motor or did you just put it together and start riding like normal?  Without seeing pics these are my initial thoughts.  Like Ace suggested, perhaps the cylinder was machined too large for the piston, the ring gaps could be too wide, or the motor wasn't run in properly and the rings didn't seat causing the cylinder to glaze.  How many times have you changed the oil since the rebuild?  Are you getting excessive blow by oil or is it all going out the exhaust?

Scottie J


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1958 RE/Indian Trailblazer 711cc

ajb235

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Re: High oil consumption on 500 classic
« Reply #5 on: April 02, 2014, 08:34:41 AM »
I used 0.004 inch clearance at the piston skirt. I do have a wet sumping issue , at most start ups, smokey for a few minutes, then clears.

ace.cafe

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Re: High oil consumption on 500 classic
« Reply #6 on: April 02, 2014, 08:46:25 AM »
I used 0.004 inch clearance at the piston skirt. I do have a wet sumping issue , at most start ups, smokey for a few minutes, then clears.


Park it with the crank position near TDC, so that the oil doesn't run out of the con rod when parked. That can help with wet-sumping.

Is the exhaust smoking a lot during riding, or are you pumping the oil out the breather? Have you done a compression test?
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ajb235

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Re: High oil consumption on 500 classic
« Reply #7 on: April 03, 2014, 03:27:06 PM »
Hi, I checked compression pressure, came up at 150 psi on wide open throttle,when cranking. Checked with my mate who followed me for 250 miles at the weekend, no smoke at at all, no smell of oil, where's it going?

RE_Chief

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Re: High oil consumption on 500 classic
« Reply #8 on: April 03, 2014, 04:27:17 PM »
I rebuilt my 94 500 last year and it took a while for the rings to bed in.  When I stopped using synthetic oil and used a slightly thicker mineral oil the oil burning finally stopped.  My compression had been raised and the motor does push a bit of oil out the breather.  My oil consumption has settled down now to comparably what it was before the engine rebuild which is approximately 1ml per km, not excessive but not as little as I had hoped.  My oil consumption will be a little getting past the rings, just normal and a little through the breather.  My breather hose goes up, over and out past my rear wheel.

Regards Charles

ace.cafe

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Re: High oil consumption on 500 classic
« Reply #9 on: April 03, 2014, 05:04:32 PM »
Hi, I checked compression pressure, came up at 150 psi on wide open throttle,when cranking. Checked with my mate who followed me for 250 miles at the weekend, no smoke at at all, no smell of oil, where's it going?
150 psi is okay for premium grade fuel, but it is a bit stiff for a stock alloy con-rod and stock bearings . Don't be too surprised if it starts knocking by 1500 more miles and needs bottom end work. I don't want to scare you but it's pretty common for that to happen.

Anyway, it's going out the breather.
So, we want to do like Charles said, and run the breather hose upwards like a "stand pipe", and then make sure that there is a good working duckbill valve on the outlet of that hose, whether it's going into a catch can or not. It must have a duckbill on it. Then, do not fill the oil tank full. Fill it to half way, and keep an eye on it. If the oil level is high, it blows more out the breather. We all use the halfway mark as the full mark. Or at most, the 3/4 mark.
see how that goes.

Oh, and no synthetic oil. Regular oil that is about 20w-50 and is motorcycle rated with sufficient(1100ppm) ZDDP content.
« Last Edit: April 03, 2014, 05:07:35 PM by ace.cafe »
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High On Octane

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Re: High oil consumption on 500 classic
« Reply #10 on: April 03, 2014, 08:20:21 PM »
On my twin if I fill to the oil tank to full mark it will puke oil out the breather too.  What I did was filled it about 3/4 full and rode around town for awhile at higher RPMs until I noticed there wasn't a significant amount of oil dripping out of the breather anymore and went back home.  Then I let the bike cool for an hour or so and cleaned all of the oil mess off of the bike and went for a short ride to double check it wasn't spitting oil and parked the bike again.  I then pulled the dipstick and used my pocket knife to etch a line where the oil level was.  Now I know not to fill above that line and I don't consume nearly as much oil as I thought I was.  It was a little below the halfway mark as well.

Scottie J


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ajb235

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Re: High oil consumption on 500 classic
« Reply #11 on: April 04, 2014, 03:10:51 AM »
OK, many thanks for the useful advice received. I'm, going to do the following, based on the comments.
1. Change my oil from 10W-40 semi synthetic to 20W-50 mineral oil with 1100ppm ZDDP( anyone recommend a good brand that I can get in the UK?)
2. re route my breather, up and over so that it vents on the chain, with a duck bill.
3. Fill my tank to 1/2 and keep an eye on it.

I do have the Alpha roller big end bearing fitted, so I'm hoping that the engine will stay together with the high compression.
The bike has always gone well, pulls like a train, so I'm hoping that your suggestions will cure the oil consumption.
Thanks agin, this is an excellent forum!