Bad compression, last chance for easy solution.

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DreamV4

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The bike I bought was not running for many years and I poured some ATF into cylinders.
I turned crank a few times and installed spark plugs.
I cranked it with starter and heard bad compression probably 2 cylinders.
I checked valve clearance, rear head was perfect, chain tension was Ok.
Tomorrow I will check front head clearance, hoping to find too tight valves.
After that I will check compression.
Any ideas, suggestions?
Is it like common car engine with oil pan? If this is so, I can remove/replace pistons.
It looks like pistons can be removed w/o removing engine.
 
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MaxMidnight

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Before doing anything you would need to establish if it is losing compression via the valves or piston rings and a cylinder leak down test would do that.

If the motor runs I would put a tin of Forte Engine Flush (or similar if not available in the US) through the system first.

Unless you want to do a full strip it may well save you a whole heap of work if it frees up gummed up rings.
 

DreamV4

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can heads and oil pan be removed w/o removing engine?
 

02GF74

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If you want to look inside the cylinders, how about an endoscope?
I bought one of these that connects to an android phone, has built in led light and although I've not used it yet, I would expect it to fit through the spark plug hole. Cheap too.
Screenshot_20210701-191334.jpg
 

02GF74

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Good on you. You'll be glad it's over and means any early signs of cancer should get caught.

That may or not bother you as we all gotta die sometime, but you will prevent those who are close to you seeing you suffer.

So anybody who is due for one, do it.

 

Fire-medic

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One of my retired co-workers just had gold 'markers' placed in his lower GI tract in-preparation for radiation therapy for his prostate. That's next.

I've had a couple multiple-needle biopsies, it's really not that-bad, I was conscious throughout, and if they find something, get it taken care-of. What I've been told, is that if you live long-enough, all males will develop CA of the prostate.
 

one2dmax

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can heads and oil pan be removed w/o removing engine?
Yes. Though it sucks getting the heads out. After they are out and if you go with some heavy duty head studs like we sell the job would be a lot easier to go back together since the studs could be put in AFTER the head is back on leaving you a lot more room to slide it in.
 

sider

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The bike I bought was not running for many years and I poured some ATF into cylinders.
I turned crank a few times and installed spark plugs.
I cranked it with starter and heard bad compression probably 2 cylinders.
I checked valve clearance, rear head was perfect, chain tension was Ok.
Tomorrow I will check front head clearance, hoping to find too tight valves.
After that I will check compression.
Any ideas, suggestions?
Is it like common car engine with oil pan? If this is so, I can remove/replace pistons.
It looks like pistons can be removed w/o removing engine.


Have you tried pouring oil into the cylinders and testing the compression? If it stays the same, then it's the piston rings, while if it improves, it's the valves that give you the problem.
If the problem is not the pistons, you clearly have to replace the valve fishes, while if it's the pistons, before replacing them (it would be of little use, because a good job requires re-bending Of the cylinders, and replacement with larger pistons and piston rings), you could try with a ceramic-based additive Be careful because ruining a "slow" .ore like that of the v-max is difficult. They may also have simply glued the piston rings to the pistons. In this case, add a good additive To clean the engine and run for 4 / 500km, and at that point try the compression test again
 

Fire-medic

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Have you tried pouring oil into the cylinders and testing the compression? If it stays the same, then it's the piston rings, (1) while if it improves, it's the valves that give you the problem.
If the problem is not the pistons, you clearly have to replace the valve fishes (2), while if it's the pistons, before replacing them (it would be of little use, because a good job requires re-bending Of the cylinders (3), and replacement with larger pistons and piston rings), you could try with a ceramic-based additive Be careful because ruining a "slow" .ore like that of the v-max (4) is difficult. They may also have simply glued the piston rings to the pistons. In this case, add a good additive To clean the engine and run for 4 / 500km, and at that point try the compression test again
(1) I think you have that backwards. Any professional mechanic wish to corroborate?

(2) definitely a translation issue, are you meaning to-say valve seats?

(3) a cylinder over-bore?

(4) not-sure what is "ruining a 'slow-bore?"
 
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Screwloose

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Not trying to contradict anyone here, just my experiences.

I find the only way to truly know what is happening inside the combustion chamber when you get low compression, is to take the head off (you would need to do that anyway in just about all cases) then pour some very light oil such as sowing machine oil on all the pistons and have a look the next day to see if the oil is going down on the low compression reading pistons, and do the same with the valves and valve seals. Over the years I've had some strange surprises with low compression when taking a head off to venture inside, and ended up doing rings, valves seats and guides. Maybe it's just my luck but I find with engines laying up for years you can only expect that amount of work, anything less is a bonus.
 

sider

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(1) I think you have that backwards. Any professional mechanic wish to corroborate?

(2) definitely a translation issue, are you meaning to-say valve seats?

(3) a cylinder over-bore?

(4) not-sure what is "ruining a 'slow-bore?"




1: If you pour oil into the engine cylinders, the oil will seal off any compression leaks caused by worn / damaged piston rings. if the compression does not improve then the pistons and piston rings are fine and the problem is the valves not closing well.



2: Yes, valve seats.



3: new engine cylinder bore with a set of pistons and piston rings, with an increased kit. (Hope this is the right translation. Unfortunately, as already mentioned, I have difficulty with technical English)



4: it is really difficult to ruin a "slow" engine like that of the vmax





Sorry for the many mistakes. It is difficult to notice the errors of the phone's autocorrect when you are not writing in your native language
 

DreamV4

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Oil in compression Up.. Rings..
Both compression tests were done after adding ATF to cylinders. first test was by "ear", second with tester 2 days later.
ATF could release stuck piston rings
 
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