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Post by justbuggin on Feb 23, 2012 0:29:49 GMT -5
great for you and thanks for sharing what you found out some times you just got to dig into it to find the problem
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Post by mainepeace on Feb 23, 2012 0:32:11 GMT -5
Great that you finally solved the problem! I think maybe a few people suggested the valves, don't really remember. However, it is odd that with the valves leaking that the compression did not go down significantly, which is a normal sign of bad valves.
Greg
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Post by carasdad on Feb 23, 2012 1:26:15 GMT -5
Greg....agree about compression. Brians dad(used to work for Rousch Racing) He did most of the testing....said even some of his Harley parts are made in China these days.....(So much for Buy a Harley....ride American huh?)..... ;D
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Post by D-cat on Feb 23, 2012 11:38:29 GMT -5
...but... duct tape is the hand man's secret weapon!
/jk Glad it's working. I'll keep this in mind as my engine ages.
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Post by tortoise on Feb 23, 2012 13:29:57 GMT -5
the valve tops themselves are weak and distort easy from the cheap pot metal they use Related 2007 thread. |
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Post by imnts2 on Feb 24, 2012 9:35:10 GMT -5
The point?
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Post by carasdad on Feb 24, 2012 10:00:27 GMT -5
the valve tops themselves are weak and distort easy from the cheap pot metal they use Related 2007 thread. Tortoise...EUREKA!...Thanks for the link! and I hope EVERYBODY reads it! VERY informative find....wonder why that never made it to this board tears ago....for all those with oil blow by probs.....who instead of fixing it...put a Band Aid on the issue. Would have saved lots of frustration for many. I am sure Chinese manufacturers did not want this publicized....AGAIN.......thanks...and ALL OF YOU with blow by issues......go read the article...then buy good forged valves..or like I did...the 'so called' titanium ones....a bit more costly....but sure beats leaving an oil trail for the cops to follow when you knock off a convenience store huh?...  |
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Post by Globs on Feb 24, 2012 11:55:34 GMT -5
Interesting fault, I would have thought dodgy valves would just add pressure back out of the intake and reduce compression.
I wonder what the mechanism for (over) pressuring the crankcase is?
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Post by carasdad on Feb 24, 2012 13:36:06 GMT -5
Interesting fault, I would have thought dodgy valves would just add pressure back out of the intake and reduce compression. I wonder what the mechanism for (over) pressuring the crankcase is? It is not over pressurizing the crank case......what happens is..the oil that exits out of your rocker arms is cast up against the opening in the valve cover that leads to the vent tube. Which is what it is designed to do...in fact it is splashed right onto that opening(crank your engine with the valve cover off and watch where the rocker arm oil sprays..RIGHT into where that vent opening is on the cover...this should help you understand)....now right behind it comes the blow by gasses...and what do they do?....push that oil up the passage and out the vent....kinda like urinating into a fan is it not?.... ;D So you see the crankcase itself is not over pressurized....and if so....would we not be blowing out crankshaft seals and crank case gaskets?....  |
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Post by voidedwarranties on Feb 25, 2012 2:44:53 GMT -5
Interesting that grinding and laping the valves fixed your problem. I won't argue with your results but, I'd say something else you did in the process of removing the head and reinstalling it fixed your problem.
Unless your valve stems and seals were shot (which you didn't replace) there is no way for "blowby" to get into the valve cover. Anything blowing past the valves will either go out your intake or exhaust.
How did your head gasket look? I'd guess it was leaking into the cam chain gallery.
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Post by rapidjim on Feb 25, 2012 10:34:34 GMT -5
Interesting that grinding and laping the valves fixed your problem. I won't argue with your results but, I'd say something else you did in the process of removing the head and reinstalling it fixed your problem. Unless your valve stems and seals were shot (which you didn't replace) there is no way for "blowby" to get into the valve cover. Anything blowing past the valves will either go out your intake or exhaust. How did your head gasket look? I'd guess it was leaking into the cam chain gallery. How so? Your valves go right through your head into the cam/valve cover area. ....so not not everything blowing past your valves goes into your intake or exhaust. Take a moment and visualize the inner working of these engines....even though the valve stems are 5mm give or take + or- the wear tolerances....high pressure can still pass through them.... Head gasket each time I tore it down was new....and how is a head gasket going to allow blow by into the valve cover. Loss of compression yes....oil leak yes...but how is that going to get into the valve cover?...  First off glad you fixed your problem! I will admit I did not read all the posts you made on this problem but, from what I am reading now, I am having a hard time believing that blowing a quart of oil out the vent in 7 to 10 miles was caused by valve seating in the combusion chamber. Here is why: www.bobistheoilguy.com/blowby.htmlWhat is Blow-by? Blow-by occurs when the explosion that occurs in your engine's combustion chamber causes fuel, air and moisture to be forced past the rings into the crankcase. Your engine's rings must maintain an excellent fit in order to contain the pressure. www.ootyscooters.com/images/Top_10_Scooter_Problems.pdfIf the overflow tube on the air box is full, drain the tube. This can be a sign of worn piston rings, a clogged transmission breather hose or other hose, incorrectly set valves, or a malfunctioning pressure breather plate in the valve cover. The hose coming off the valve cover vents the entire engine of any vapor that occurs in the engine - either gases from the engine oil or any blow by past the rings. There are supposed to be baffles in the valve cover to help stop the flow of oil into this tube. Before EPA, this tube would be vented into the atmosphere. Now the tube vents into the air box so the vapor can be burned in the engine. If oil is getting into the air box it is either being pushed by too much pressure in the crankcase (blowby) or being sucked there by the vacuum created in the air box by the carburetor. Sometimes it could be a combination of both. You could remove the hose from the air box and let it vent into the atmosphere for testing. If this stops the oil from flowing out the vent, we know it was being sucked out. If the oil runs out the hose then we know that too much pressure in the crankcase is pushing it out. If this is the case, check and make sure the baffle plate is in the valve cover. Whatever it was, the main thing is it is fixed!!! Jim |
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Post by carasdad on Feb 25, 2012 11:08:46 GMT -5
Everybody is a critic and expert....yet NOT one has fixed their blow by problem except with a long line...fuel filter and the good grace of God...or an oil catch you have to drain every 100 miles... then somebody comes along...with the solution...and a link to an article that explains it....and he is considered the fool? In my native language(Chippewa)....I must say this...> hokecheenie waa lasa behini nota leasii .....gonemaseya si i jeka konitameya chon beda mita....
Translation...a fool is one that does not listen to learn...the biggest fool is one who chooses to speak when he should listen to learn...(Chippewa again)...yo sesa hagachi mela obanee kiki ...shendago soochie a lia dedee scooter.... (translation) if you are such a God with will all the knowledge...why have you not fixed all the problems our brothers have with their scooter? What i did worked for me...so I shared it...yet you persecute my findings?... Show me your "Chinese scooter expert certificate"...inbox it to me...you God of all Gods...and I promise to build a shrine in your honor...we prefer to build with Blue Spruce...since the needles do not fall off with age..
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Post by Globs on Feb 25, 2012 11:47:54 GMT -5
I can see an internet fight developing here but I have no idea why?!
People are just curious and this is just a discussion thread, not life or death, so could we all chill out a bit please?
Thanks in advance!
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Post by Pony66 on Feb 25, 2012 12:18:58 GMT -5
Hopefully there is no fight, just an interesting debate.
Im thinking that the OP may have experienced a failed valve stem seal. (maybe not). I usually see them resulting in running smokey. However on this horizontal cylinder, it could result in pressurizing the valve cover???
BTW, the EPA didnt end the "road draft" vent tube. It ended by better design with the PCV tube in the mid 60's. It does work very well, the EPA did rule it illegal to remove the PCV.
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