Author Topic: Top end  (Read 3573 times)

powerplay

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Top end
« on: April 06, 2009, 08:57:14 AM »
took the top of the engine off today and removed the engine from the pilot. Its the main bearings that have gone, the rest of the top end looks very good. There is no marking on the piston, does this mean its standard
size? it measures 80mm.

PilotHawK

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Top end
« Reply #1 on: April 06, 2009, 11:34:08 AM »
The top-end doesn't look too bad. There is some wear around the exhaust port, but the piston top looks good. Did you clean the dome on the head? I would measure the piston and cylinder and compare them to spec. if they are good I'd knock the glaze off the cylinder with a good hone, and install new rings and run it. Stick with an ART piston (OEM) and high quality NSK, Koyo or OEM bearings. Use oem seals and gaskets if possible.


Weed is a great source for any part you would ever need to upgrade or repair your pilot.

http://www.pilotodysseyperformance.com/

If he doesn't have it listed shoot him an email and he'll find it for you.

This might help you along you journey of rebuilding the motor.

http://g2buggy.g2-innovations.com/gentech/manuals/topend_rebuild.pdf

http://g2buggy.g2-innovations.com/gentech/manuals/2stroketunershandbook.pdf

powerplay

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Some more questions
« Reply #2 on: April 07, 2009, 10:19:17 AM »
Pilothawk, Could you advise me on the best way to break a pilot in, and also, i am considering buying a new clutch (as i bent my sons talking it off)
What are the differences in the comet and the powerblock?

PilotHawK

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Top end
« Reply #3 on: April 07, 2009, 11:09:55 AM »
I would read up on the gordon jennings stuff in the previous links I posted. I run in an engine the following way and it has worked for me.

After you have everything together start the engine and let it warm up, In the pilot I let mine go until the fan kicks on. Just let it idle when doing this.

After the fan comes on turn the pilot off and let the engine cool off completely. Once its cool I check everything and retorque the head nuts and cylinder base nuts.

After that I warm it back up to operating temperature then run it like I stole it.

Others advocate several heat and cool cycles and varied operating speeds for 2 or 3 tanks of fuel then run it like you normally would,

Weed

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Top end
« Reply #4 on: April 07, 2009, 08:37:11 PM »
Powerplay

I got your email.....but didn't read your post first.  80.00mm is the standard bore.

As far as boring the cylinder, you will need to determine if it needs it.  

Can you feel a grove on the top of the cylinder where the piston ring stops?  Do you have access to a micrometer or dial bore indicator?  You will need to measure the area where the piston ring stops on the top of the stroke(that is where the most wear occurs).  And you need to check for roundness of the cylinder bore.

I hope this helps and not confuses you...

powerplay

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cylider
« Reply #5 on: April 07, 2009, 11:39:44 PM »
The cylinder has no lip on the top edge, i am no engineer and have very little experince with 2 strokes but i am a ex motorsport mechanic. (cosworth) i would say the cyliner must have been changed recently or its not been used very often, I would think a new set of rings and rod, bearings and pins would do the top end nicely. So if you could give me a price difference (without the piston) i can get the stuff ordered and hopefully get it running again :D  Also i am considering changingf the clutch, what would the postage be for one of your comet clutched to Bulgaria?

Thanks

Stuart

Adnoh

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Top end
« Reply #6 on: April 08, 2009, 06:48:14 PM »
Hi power play this is Adnoh. I'am a pilot guy and like your self like to play with motors. It sure looked like you had some piston rock going on in the pics. Since your going to rering the piston. Pull the bottom ring off and use the skirt of the piston to push dwn the cylinde and measure the gap in several places.  Starting at the bottom of the jug ans use that as you base lin the work toward the top. This will give you an idea of cylinder ware You may be surprised. If there hardly any change in end cap you can use you new ring and compare as well check to see if the end gap is in spec with out boring. No mater what if you rering have it honed and replace the piston pin and bearing. The end gap spec for stock rings are.018 to .024. I post up some pics from manule you can use as a guide and see what I mean.

Weed

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Top end
« Reply #7 on: April 08, 2009, 09:47:26 PM »
Powerplay,

you should have an email from me.

I forgot to add the piston pin(if we decide to just re-ring) and the total will be $14 more than what I quoted.

Adnoh is the Pilot guy around here......he will get you headed in the right direction.

Weed

powerplay

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Top end
« Reply #8 on: April 09, 2009, 09:28:25 AM »
thanks Adnoh i found that very useful, couldnt find my feeler gauges but will check the cylinder when i find them. Mean while my own pilots not sounding too great this i will take the head off tomorrow and see what its like and if need be do the top end on that at the same time.

Adnoh

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Top end
« Reply #9 on: April 09, 2009, 03:36:09 PM »
Before takeing off head check you cranking pressure with a compression guage. this will give you indacation of the condition. As pilot Hawk mentioned use the spec I posted out of the maunal to check over motor.
I can post up other info if you need and I think Pilot hawk has a pdf version for the pilot. A good book come in midy handy. If you would post up pic of that head as well, Thanks. The flow pattern on the first one looks good.

P.S. have fun doing the work. I find it relaxing.

PilotHawK

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Top end
« Reply #10 on: April 09, 2009, 04:37:58 PM »

powerplay

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pilot
« Reply #11 on: April 10, 2009, 03:15:27 AM »
lol :lol:  i would find it relaxing if, i was not in the workshop all the time building this! Both pilots have been fine all winter, its typical when the weather is beautiful they have to break down :lol: I ordered a oem hard copy of the manual, as the pictures on the one i have are pretty bad.
Its a shame there is no direct replacement for the pilot engine, something around the cbr600 would be nice (and reliable) maybe one day i will have a go at doing a pilot with manual gears and a 600 cbr in it. Meanwhile this one i am building is powered by a 2007 cbr1000rr motor. I built the frame from scrach. was pretty dificult to get the engine to fit!

powerplay

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top end
« Reply #12 on: April 10, 2009, 04:22:41 AM »
Found my gauges the rings are measuring 0.70mm in all area tried a 0.75mm feeler and it wont fit in. Done a compression check on the other pilot and its down at 132psi  also it looks like its running to weak. could this be down to the fact its still got its winter spark plug in? I have removed the head and cylinder, the ring end gap is 0.58 looks like this one has not long been rebuilt either, again its on its standard size oem piston and the cylinder looks like its not long been honed, i will tak some pictures and post them.

Adnoh

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Top end
« Reply #13 on: April 10, 2009, 06:52:13 AM »
I looked over your pics and must say you have a lot of good ideas there. I like the rack and upper shock mount on rear trailing arm( shocks cheaper). I could go on from there. I would like to list most of your rework for furture projects if you do not mind. Then you can comment on them and how well the worked. You shuld start a project thread for us here to enjoy and borrow,steal some of your ideas. Where to start front or rear. Do you have the old pilot steering componets. There is a handy capped guy that bouhgt a drake and need pilot steering wheel and controls. He would be a good canadate for the slavaged parts. Oh ya this is about the motor. 138 is low. the ring end gap as you noticed is way out and must likly need to be bored. This would account for what look like piston rock ( slap) in the cylinder. I bet it a little out of round. Ill post up some pics using a chaep tool ( ten buck) to do quick check before spending money. The tolls have many uses.

hoodlum

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Re: top end
« Reply #14 on: April 10, 2009, 07:09:01 AM »
Quote from: powerplay
Found my gauges the rings are measuring 0.70mm in all area tried a 0.75mm feeler and it wont fit in. Done a compression check on the other pilot and its down at 132psi  also it looks like its running to weak. could this be down to the fact its still got its winter spark plug in? I have removed the head and cylinder, the ring end gap is 0.58 looks like this one has not long been rebuilt either, again its on its standard size oem piston and the cylinder looks like its not long been honed, i will tak some pictures and post them.[/quote                                  



It also needs to be measured for out of round,which can't be done with rings...A bore gauge is needed for that...
Hoodlum