Valve Job. 150CC GY6 By imnts2 (Read 3,986 times)

[imnts2]

I have decided to try doing a valve job on my 150CC GY6. Any tips from anyone. I have had the head off before so that is not a concern. I don't have a valve spring compressor. Do I need one or is there a way to do it with out? I thin the rest is pretty straight forward. Thanks of any input.

lefty2

[Alleyoop]

Heck Lefty2,
If you have taken the head off SHOOT adjusting the valves is a piece of cake.
adjust the top Intake to .004" and bottom Exahust to .005".
Here is a video
Alleyoop

[Kaveman]

A valve spring compressor ( briggs and stratton small engine type works best) will make things much easier . There are 2 springs on each valve (inner and outter) and trying to get the retainer caps parts off and on by hand will just get you frusterated. There is also the valve stim guides you will need to watch for when the springs and valves are off the head aswell. Look at a used tools store or a pawn shop and you might get lucky and find one cheap.
will

[sprocket]

Valve Job??? or Valve adjustment??

Valve Job...

Just replace the head... if the valves need a valve job, then stem guides and springs are also on their way out...

I always figure 5000++ miles and $150 parts and labour, to do a particular job...

REPLACE the engine... $250++

You will be MUCH further ahead...

[tvnacman]

You might be better off replacing the head . There is a kit head , jug , oil pump , gaskits . rollers and orings . For like $75 + shipping , the head with valves go for about $50 + shipping .

John

[imnts2]

Hi Alleyopp. I am an old mechanic. (81) So I really meant "valve job". I hope to get by with just lapping the intake. Yes, I thnk if I really needed a valve job replacing the head is the best answer. While at it cylinder and piston. Frankly, I an planning to sell it. I have replaced it with a Majesty to keep the 4 wheelers from killing me.

Thanks to allyoop, shalom, sprocket and tvnacman. I have bumped into all of you before and have learned to respect your knowledge and information. Got almost everyone I wanted to hear from. I will bend your ears a little hoping to gather some more wisdom.

First my reason for tackling the valves. The scoot was shipped without cooling shrouds (I think) It had about 600 short trip miles when I got it and I put another 100 before I figured out it needed and got them on. Now have about 1500.
I did a compression check (harbor freight gauges) Only about 110-100 psi (of course that could be the valve on the gauge not shutting as quickly as is needed for on a small cylinder) I also have a "harsh" almost piston slap noise on near full to full throttle and a top of about 48 GPS level/no wind and having wife follow me with a speedo I have calibrated a several different times/places on the interstate (10 mile markers with a good stop watch) I have it holdiing valve adjustment good and starting promptly, hot, cold(about freezing). It also is a real lazy dog on acceration.
I have slipped a 114 main jet in and she runs just a little rich. Seems to like the 110 stock a little better. Does seem to need the idle out 4 turns to idle decent (Maybe a little leakage on Intake? (I have done a propane test for manifold leak)
So part of the reason is to learn what I learn. Gotta know you know.

1. I will find out it the valves are not seating or if the piston is slapping. If I have better compression pressures when assembled etc. Maybe I will get rid of the noise (course she is naked so you hear everything.)
2. I will feel better being able to represent it more accurately when I sell it.
3. It would be nice to get a chance to ride it when it runs right.

I have opened the CVT and made sure it is clean and run in on the center stand and it seems nice and smooth.

Question to shalom. I uses to have a C type comprssor I used to do chevy/GMC/Nash 6's and Jauguar heads. Work or to bulky? Hock shop is a good idea.

Again thanks. really appreciate the expertise. Glad I found where you are all hanging out. Owe you a cool one.

lefty2

[tvnacman]

Imnts2
What size wheels and what weight rollers are you running ? I have a scooter with 16" wheels I had some carb problems , I changed the carb twice . I noticed the first time around it solved a burping farting problem , but it felt held back . About a year later or less the new carb started acting up . I changed for a keihin all of a sudden it was like the engine woke up . I'm thinking the low priced carbs maybe your problem . Inmts2 I'm half your age , pops would say first its not the car its the driver , the other thing he would say the power is in the carb .

Its funny for you to mention rambler , I just had a conversation about it yesterday .

Mic the width of that chino belt , I had one rip apart in like a mile and a half .

John

[Alleyoop]

Sorry Lefty2,
I read it wrong, that is why I said crap if you took and put on a head adjusting valves you should be able to do it in your sleep(HAHA). Well you have 11 on me so I am right behind you but I will never catch you. Good to have another wrencher, as for the slapping doesn't sound good I would guess crank slop or the wrist pin.
Alleyoop

[tvnacman]

recheck the valve adjustment .

John

[Bashan]

If you do decide to do the lapping some pictures of the procedure would be nice, We've got one post on that in the engine section but another perspective would be great, The current thinking is if the valves are toast just get a ready to go head with everything installed. I think it's nice to take your time and rebuild it so you can make sure everything is right even if you don't save any money that way. JMO, Rich

[imnts2]

The reference to Nash was the old overhead valve Ambassador 6.

Agian thanks to everyone.

I have decided to open today. Pull the head, turn it so I can pour a little lacquer thinner in it and see how bad each valve leaks. I am pretty sure I have a valve leaking and it only takes a little intake valve leaking to lean out hard throttle mixture and cause preignition.. I'll let you know.
While it is open see if I can find any play in either end of the rod. Measure the piston and bore and look for signs of slap. Oil stays very clean
Then make a decisiion. I will keep you informed.
Rich If I lap you will get some good digital pics.

Been fun.

lefty2

[imnts2]

::I was wrong! All my theory was just that - theory. Neither the intake or exhaust valves have any discernible leakage. I blocked the head upside down , level, covered both valve heads with lacquer thinner and not a drop leaked. So it is not blowing back into the intake.

carefully miked the piston and the cylinder and do not find anything wrong. And no signs of piston scuffing of the cylinder wall or the piston itself. In fact it is so well polished it might even be glazed.

and I cannot get any slack movement out of either the upper or lower rod bearings or the crank bearings.

So I will run the hone thought the cylinder, slip a new set of rings in and reassemble and break in quickly.

The next step after reassemble will be to get a tach on it so we can tell RPMs more accurately than my ears although. I am guessing the clutch engages about 3000 and she runns to about 5 Grand on the highway and about 8 on the stand. Lets find out.

Any favorites for a reasonably priced accurate tach?

Cheers
lefty2

[sprocket]

Accurate and reasonable.. no...one that will last you 10 scooters and does so much more... a Trail Tech...Vapor

trailtech.net/vapor.html

[imnts2]

Good lead sprocket. But I think I want a shop tool. I woud think a conventional tach/dwell meter would be fairly usefull and an inductive timing light would allow me to see the timing and advance curve. Together I would be able to get a reasonably accuate map. Good enough fer a good enough country boy. Yes?

[imnts2]

OK time for a quick report. once it opened up, I could not find anything out of sorts. Bore and piston miked like new. I filled the head with lacquer thinner and waited a day with only a little leakage. So a set of cheap rings, gaskets and spark plug were ordered. After de-glazeing she was assembeled. It took forever to get the rear brake properly bled. (finally removed the caliper to get a straight loop. That and with better half's help I got it).

Amazing. I only have abour 5 miles on it now. The enginel stops quick and tight when the ignition is turned off so I am still ony thinking it is really fixed. But the hammering that has been around for a coupts of months is gone (for now at least) And goodness it runs. 0 to 40 (real) is nice and strong. Not a match for the Majesty, but really fun. So much better -. So far, I am limiting it to 40 until it gets most of 100 mles on it although today I caught it creeping up a little.

plan to change oil at 100 miles.