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-   -   Oil Starvation in front cylinder ? (https://www.vn750.com/forum/31-engine-exhaust-cooling/91098-oil-starvation-front-cylinder.html)

m9e8n7k6e5 02-14-2017 09:43 PM

Oil Starvation in front cylinder ?
 
Ok, So I did a full rebuild on this motor 9 years and 75k miles ago. I started getting some top end noise recently and decided to use the cold months to investigate.

Here is what I found: Rear Head everything is perfect and within inspection limits

Front Head:
scoring and excessive wear on cam journals
all 4 tappets are frozen

Rocker wear is as expected

The microfilter appears to be no dirtier than rear.

At this point I have to replace the front head/ cams as they are too far gone, but I certainly want to ensure whatever caused this does not happen again.


What might be causing this type of oil starvation in only one head?

Spockster 02-14-2017 11:09 PM

Clogged oil galley that feeds the front? Haven't found an oil flow diagram yet. The rear head is fed through the external oil line, correct?

I did check the head and base gaskets in case there was a difference, all have the same part number.

The oil pump apparently is working enough to feed the rear cylinder and crank.

Spockster 02-15-2017 12:55 PM

Ok, found the oil flow diagram in the downloaded manual, under Engine Lubrication 6-3. If the drawing is accurate, both heads are fed from the oil line off the front of the engine where the oil pressure switch is located.

I would check to be sure the line to the front head isn't clogged and also find a way to verify flow through the micro filter, or simply replace both. Color of those filters is not a good indicator of porosity. Barring a problem with either of those, I would say the oil passage in the front head must be clogged.

Spockster 02-15-2017 01:21 PM

One more thing, though not sure it's possible.... Be sure parts that mount on top of the cams haven't been mixed up. (forget what they're called) All it takes is one hole being covered to stop oil flow.

m9e8n7k6e5 02-15-2017 01:35 PM

it is easy enough to replace those little filters, so I will do that.

I have the Cams out, I suppose I can take the cam chains out, put enough oil in it for the pump to pick it up, then turn it over on the bench with the starter?

It would not be the same as actually running the bike, but I imagine I should be able to visually inspect the flow from the front vs rear head ?

I may also try flushing all the oil lines/ galleys with kerosene as well?

Do you see any harm in ay of that ?

Spockster 02-15-2017 02:07 PM

That's all a good idea. Need at least one plug out of each cylinder.

Crank in bursts and watch for oil flow, keep an eye on the starter/cable temperature.

Kerosene flush is good, as long as you're not washing large amounts of external dirt/grit into the crankcase. If you could inject it into the line or passage would be good. Compressed air helps too.

m9e8n7k6e5 02-15-2017 02:46 PM

I did do a good degreasing of the engine before I starting taking stuff apart. I think I should be good on not getting more crud introduced. I hope at least.

I am going to try and flush/ test either tonight or tomorrow after work. Ill let you know what I find.


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