excessive pressure in the crankcase - Honda Shadow Forums : Shadow Motorcycle Forum
 
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post #1 of 10 (permalink) Old 03-19-2017, 02:18 PM Thread Starter
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excessive pressure in the crankcase

this is the second honda in my life and it came to me too tired. so the problem is- high oil consuption, smoke from pipes and when after a ride I open a filling cap , too much gasses are running away. When i disconnect i rubber pipe from a rear head cover there are no air moving , but they should i m sure. So what is it? is it a problem with the breather or something? i dont know is there any valve in a rear head cover. I suppose i should dismount the engine because the frame does not let me to dismount the head cover

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post #2 of 10 (permalink) Old 03-19-2017, 02:24 PM
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Remember to remind us old guys with bad memories which bike it is.


Only a biker knows why a dog sticks his head out of a car window.
1983 750 Shadow
From the past=
1951 Cushman scooter
1962 Honda 305 Dream
1965 Honda 305 Dream
1971 Honda 175 scrambler
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post #3 of 10 (permalink) Old 03-19-2017, 02:46 PM
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I would do a leak-down compression test to determine if the piston rings are bad.

If the rings are bad, gasses from the combustion cycle would leak past the rings into the crankcase.
High oil consumption could also be a sign of bad piston rings.

Good luck,
Phil


1973 Yamaha RD-350


Sterling Heights, Michigan
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post #4 of 10 (permalink) Old 03-19-2017, 02:46 PM
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Make sure your crankcase vent is open. Not sure of your bike, but your service manual should show you where it's located. It's usually on the lower right in front of the swing arm pivot.

2007 Shadow Spirit VT750C2, Ride bell by h13man, Ride cross by Capt D
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post #5 of 10 (permalink) Old 03-19-2017, 03:04 PM
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Here is a photo of my 1983 750 engine vent system if that is the bike you were refering to. The vent pipe on top of the cylinder hear has no valve and should be free flowing. Then the vapor goes through a liquid separator tank and the vapor continues on to be re-burned into the air filter box. The tank can be drained of liquid periodically. A little bit of liquid drained is normal.
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Only a biker knows why a dog sticks his head out of a car window.
1983 750 Shadow
From the past=
1951 Cushman scooter
1962 Honda 305 Dream
1965 Honda 305 Dream
1971 Honda 175 scrambler
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post #6 of 10 (permalink) Old 03-20-2017, 04:39 PM Thread Starter
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The bike is Honda VT 750 c 86 according to documents. I saw something like tube on the back side of rear cylinder , that connects crankcase with a head. It seems to me that it's jammed or something, because the pressure in case does not go through it into the head and after throughout the breather into the frame
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post #7 of 10 (permalink) Old 03-20-2017, 04:41 PM Thread Starter
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An addition - I saw a tube in manual. I don't know whether it is there. Tomorrow I'll dismount the engine
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post #8 of 10 (permalink) Old 03-20-2017, 09:17 PM
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According to the 1986 manual there is a short vent host to the air chamber on top of the head. So maybe if you have an air compressor you could blow a little air into the top of the cylinder head pipe, and with the oil dip stick out, see if it goes into the crankcase area easily. I seems to me that if you have an engine problem with too much blow by it would have a lot of oil in the air cleaner and that vent tube.
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Only a biker knows why a dog sticks his head out of a car window.
1983 750 Shadow
From the past=
1951 Cushman scooter
1962 Honda 305 Dream
1965 Honda 305 Dream
1971 Honda 175 scrambler
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post #9 of 10 (permalink) Old 04-08-2017, 11:49 AM Thread Starter
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good day (or evening) comrades. I pulled out an engine last week , but again i didnt have enough time to dismount rear cylinder. At last ive sent all the minor deals and started to do it. The first wonder was- when i dismounted the rear head cover i saw washers under the hydraulic lifters, but the are of different thickness AND THE QUANTITY WAS DIFFERENT!!! and to my regret i messed them. so now the first problem is - i dunno to which compensator i should attach them. I opened the parts ordering portal where all the engine schemes are but i saw only one washer under each lifter. Who can tell me what is the quantity of washers and why i saw a few of different thickness. the second problem is - as I understood u should at first dismount the sproket from the camshaft and only then u pul out the cam, right? but one of the sptocket bolts us in upper position and the other is in low and i can not rotate the shaft to remove them
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post #10 of 10 (permalink) Old 04-08-2017, 11:52 AM Thread Starter
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and again I realised that the honda engenereng is very complicated. Suza is more easier to servise, more friendly to a user Id say

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