Lapping my Cylinder Head (TZR 125)

[binge]

Right, The TZR Pit keeps over heating. I can only put it down to either the Air leak, which I found today. Or a head gasket issue.

It's over heated a few times, So the head is going to be warped I guess?

I need it running by Sunday (Track day), So rather than let a machine shop skim the head, as my local machinist takes about 3 fucking months to do a re-bore. I was going to try lapping it down myself with a pane of glass and some grinding paste.


What exactly do I need?

I've got an old door from work, (It's currently at work), Which I can use for my flat piece of glass. It's got a big double glazed window in it.

Got my head of course.

What sort of grinding paste do I need?




Ben

[Pete.]

Grinding paste will lap the glass as well as the head, which will end-up dishing the head. You need to get the sheet of glass and some wet & dry, then soak both and use a scraper as a squeegie to stick the paper to the glass with the water, and use that for your lapping.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[binge]

Argh I can see this all going terribly wrong. 6 days before my fucking track day too.



Ben

[Pete.]

What you got for a radiator? the TZR one?
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[stinkwheel]

Fine grinding paste. Light engine oil. A really thick, flat piece of glass. A drum of solvent (paraffin/white spirit/diesel). An old bucket/washing up basin. A paintbrush is handy. Something good on the radio. A comfy cushion to sit on.

Put the glass down on a solid, flat surface (floor?). I usually put a bit of that rubber matting you use to stop panniers rubbing your paintwork under it to stop it slipping about.

Smear grinding paste onto the glass and add a few drops of oil. Place the head on it and start swirling it about. Don't press down on it, just move it round by sideways pressure and keep rotating it every so often so you don't inadvertantly concentrate on one part. Make sure after a few swirls that the whole bit of glass you're using is evenly covered in a very thin layer of grinding paste.

Keep at it, it takes ages. You may need to add more oil and grinding paste.

Check it periodically by wiping the paste off the facing with a rag soaked in solvent (eg paraffin/WD40/diesel) and see if it's an even texture all over.
A bit like this:
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image035.jpg

When you're done, it gets really difficult to move the head on the glass.

Obviously, you then need to get every tiniest trace of grinding paste off it and out of the nooks and crannies. Lots of washing in soapy water then several changes of paraffin and blowing through of coolant passages/sparkplug holes.

It is absolutely forbidden to put it in the dishwasher because this would be totally unhygeinic.

EDIT: Pete.s idea seems better though. The above was taught to me by an old feller who used to do it on old brit bikes.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[binge]

[jimspeed]

when i do the tdi vnt turbo bits at work i use a nice heavy piece of glass with very fine wet and dry paper (400 grit or so) wet it all so the paper sticks to the glass and gently run the head over it in circular movements and keep putting lots of water on the paper.. similar process to stinkwheels but using paper instead of grinding paste..
if the bits are alloy be very careful as it is easy to get carried away and remove far too much off them
____________________
Hyosung cruise 125(passed test on, sold) Kawasaki el 252 (better than expected but sold on) Kawasaki GPZ500S first "big"bike.(sold) ZZR600 E5..Z750 2007,ER5, currently on a 2008 Enfield bullet electra x and loving it..
,"Alpha-9: Is there any correlation between dyno rod and dyno kits?"

[binge]

Okay, So assuming I use the wet and dry method. How long does it take?




Ben

[Odie]

[binge]

What I'm saying is.
Will it take me an hour? 3 hours, A whole day?

Need a rough guide because I've got a track day Sunday. And I'm considering just riding it as it is, And blowing it to bits. It's due a rebuild anyway.

[jimspeed]

i would buget 2 hours rubbing if its not too warped and maybe 4 if its really bad
____________________
Hyosung cruise 125(passed test on, sold) Kawasaki el 252 (better than expected but sold on) Kawasaki GPZ500S first "big"bike.(sold) ZZR600 E5..Z750 2007,ER5, currently on a 2008 Enfield bullet electra x and loving it..
,"Alpha-9: Is there any correlation between dyno rod and dyno kits?"

[cagiva gezzer]

I've done my cagiva once using valve paste. Unsure of the grade, but it was pretty fine. I know it's not the perfect method, but it's worked for me.

Start by rubbing a very fine layer of paste over the cylinder head . A very very fine layer as if you were greasing it. Place the head onto the cylinder and press gently and move in a very small circular motion. Just enough to seat it. Pull the head off and note how much has transferred from the cylinder to the head.

You'll see from the above photo that there are green spots where transfer has occurred and plain spots where no transfer has occurred. (High and low spots).

Put the head back on to the cylinder and gently rub the head in a small circular motion to file away the high spots. As per the above posts, clean off the abrasives with solvent once in a while to see how much is being taken off. Repeat step one to monitor the high / low spots.

Once complete it will look like the above with even transfer of paste.
____________________
"because one stroke isnt enough and four strokes waste two"

[Pete.]

Lapping should take 20 minutes on wet& dry. Is this your pitbike?
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[binge]

Yea its on my pit bike Pete.

I've just fitted a new inlet. Hopefully it will be okay. It's a piece of plastic pipe. Like the bottom one in this picture:

https://www.ted-kyte.com/3D/Pictures/Plastic%20Pipe%20Fittings%204%20Inch.jpg


But without one of the shoulders.

Looks a bit bodgey, But it's actually a PERFECT fit. You couldnt get better if you tried.
I picked it up in B&Q tonight while I was getting some Jubilee clips.


The shouldered end slots onto the carb nice and tightly. Rubber O-ring in the recess on the carb creates a perfect seal.
The un-shouldered end pushes very tightly into the rubber inlet on the engine.

Internal bore on this is bigger than the old inlet I made up. It's probably got a 32mm internal bore. Carb is a 28mm Dellorto.

I took the bike for a spin. It revs up ALOT faster now, I mean, Extremely fast.
It's got more low down punch, But it goes flat quite quickly now, higher in the rev range.

Guess this is just down to inlet difference.


Bike didn't seem to get as hot, But it didnt get a good run so I cant be sure yet.


Gonna give the lapping a miss until after my Track day at Stretton. Dont want to shit out because I was being inpatient.

After Stretton, Im gonna get a new piston kit (1mm oversize), Have the barrel re-bored, and maybe get the head skimmed. With a bit of luck it will transform the bike.





Ben

[Pete.]

There's your answer then, air leak at the inlet causing a lean condition making your bike overheat. Lucky you didn't nip it up
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[binge]

[Pete.]

There's a very good chance that it will attack the plastic. Most likely embrittle it until it cracks.

If your cylinder is not badly damaged I have a hone you can run through it if you like.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[binge]

I'll strip it down after the track day, and see what it looks like. Honing it will save going up a piston size I guess. Cheers for the offer dude.

As for the inlet, I may nip to B&Q, And buy another one of these plastic joiners. Take it round to a few fabricators and see if anybody can make up something the same out of ally.



Ben

[binge]

Also, The bike has stopped over heating!
Done about 50 miles on it tonight. Not had any problems! Well chuffed.

Still, It's definitely down on compression as it's lacking power.


A hone / Re-bore. New piston kit and rings. And skimming the cylinder head, Should give it a new lease of power.