Piston kit, where from?

[LittleJohn]

From what I have read here they can be honed but I personally wouldn't let a hone within a hundred meters of a nicasil bore read this thread on Chamchains experiences! http://www.kiwibiker.co.nz/forums/sh...t=26429&page=2

Am in agreement with a lot of that thread (except putting a scotch brite down there). There are some things that need to be considered.

A barrel doesn't need to be honed everytime but done when it is needed. Honing a barrel can prolong it's life (yes it does, when done properly) and can prolong your pistons life (reduces the amount scatches on the sides of the piston).

A lot of people in various threads have said about this guys from the whops who can do this, or I went to this place and this happened. Although there maybe people and places out there that are really good, they need to be better than that. I would, and do only use Engine Specialists on the Shore. They look after race engines, both motorbike and cars, also some of them are riders. Not only can they do the honing they also do resleeving etc.... so they know what they are doing.

At the end of the day it is up to each perosn as to whether they want to hone a barrel (but I would never put scotch brites or sand-paper down it like some poeple), if you are going to hone it make sure the people who are dong it are the best, and know what they are doing.

[Reckless]

Agree with alot of what you say Littlejohn and our posts probably indicate the two different camps on this honing thing.
I was always lead to believe that nikasil was for the life of the engine (from advertising in the days it was first introduced) with proper maintenance (cleaning filters, doing rings etc etc). Pretty much that has been proven to be true as well. As I've had some very overstressed 125-2smokers in my karts on methanol, with high compressions and moto plat ignitions etc.
I simply don't see the point in taking 50 new pistons/reconditions worth of life out of the nikasil coating with a hone for what may be a negligible gain in performance in the short term because next time you do a piston (50-100 hours on in a Enduro bike) generally the bore looks pretty much the same as before you previously honed it in my humble opinion. I suppose if your guys are only honing hard enough to take the highs off the barrell this would be ok.

I do take your point on the piston skirt wearing less if the barrell is smoother that makes sense, but I'd rather wear the piston than the bore with a hone. After all isn't this the main principal in using nicasil ie hard coating Vs soft ring and piston?
Anyway we'll probably have to agree to disagree and there's no problem in that either. Cheers mate good discussion, Cya out there on the trails!

[LittleJohn]

Agree with alot of what you say Littlejohn and our posts probably indicate the two different camps on this honing thing.
I was always lead to believe that nikasil was for the life of the engine (from advertising in the days it was first introduced) with proper maintenance (cleaning filters, doing rings etc etc). Pretty much that has been proven to be true as well. As I've had some very overstressed 125-2smokers in my karts on methanol, with high compressions and moto plat ignitions etc.
I simply don't see the point in taking 50 new pistons/reconditions worth of life out of the nikasil coating with a hone for what may be a negligible gain in performance in the short term because next time you do a piston (50-100 hours on in a Enduro bike) generally the bore looks pretty much the same as before you previously honed it in my humble opinion. I suppose if your guys are only honing hard enough to take the highs off the barrell this would be ok.

I do take your point on the piston skirt wearing less if the barrell is smoother that makes sense, but I'd rather wear the piston than the bore with a hone. After all isn't this the main principal in using nicasil ie hard coating Vs soft ring and piston?
Anyway we'll probably have to agree to disagree and there's no problem in that either. Cheers mate good discussion, Cya out there on the trails!

Also agree to disagree, both sides of the fence have valid points.
Hope to catch up one day mate.

[tommorth]

interesting stuff
they guy who machined the p/v ports after my cyl had been repaired (welded and replated) instructed me to give the bottom edges of the piston skirt a quick sand to take the edges off and give very light scuff over the bore

[camchain]

Reckless pretty much nailed what I would say about honing a nicasil bore but I'll jump in with some extra bits.

I can certainly see the advantage of having a perfectly prepared surface finish for perfect ring bed in & perfect oil cling for lubricating etc.
Problem is you always come up against the tiny nicasil wear limit. KTM spec being 0.025mm. Said it before but this is about half the thickness of a human hair - a truly miniscule amount of material to muck around with. If you go chasing scratch lines in the bore you're asking for trouble. Half the useful life of your cylinder coating can be gone in a few seconds of 'light' honing. I reckon the 'grand canyon' on ring end gaps makes those bore scratches pretty insignificant in comparison.

I'm wary of the 'H' word and would suggest anyone considering it should very accurately measure their cylinder first - quite a tricky thing to do in itself, even with the best instruments. Need to also be mindful that cylinders don't wear evenly, especially a 2 stroke down at port height due to much less bore material.

I especially don't like the idea of ball/grape or flapper type hones as it seems to me you risk damaging the coating on the port edges.
I've never seen one of these expensive diamond hone machines but I think you're dealing with a very different animal there. I'd say a great deal of accuracy could be had with one of these and you're likely to end up with a better surface as well. Don't quote me (and buggered if I know if it even matters much) but I seem to recall reading that other type hones can tend to gall up (microscopically) the bore surface somewhat. An oil molecule might appreciate the difference?

As far as using a scotchbrite pad goes, I was initially very hesitant with it but it worked well. My bore was pretty grubby and I'd much rather remove any glaze by hand than with any type of hone. It's slow but you can see exactly what you're doing. Light pressure and some CRC is all that's needed to break up the glaze. Once through that I finished with paper towels and turps until spotless.

Pays to check even brand new parts alright tommorth. I checked ring lands etc for edge dings and slightly relieved the very sharp edges on new piston. Found a nasty little ding on skirt edge and gave it some extra attention. I even cleaned the new wrist pin bearing even though it came pre-oiled in sealed plastic. Bunch of tiny shinies came off it. Factories/machine shops are not clean places.

[LittleJohn]

Reckless pretty much nailed what I would say about honing a nicasil bore but I'll jump in with some extra bits.

I can certainly see the advantage of having a perfectly prepared surface finish for perfect ring bed in & perfect oil cling for lubricating etc.
Problem is you always come up against the tiny nicasil wear limit. KTM spec being 0.025mm. Said it before but this is about half the thickness of a human hair - a truly miniscule amount of material to muck around with. If you go chasing scratch lines in the bore you're asking for trouble. Half the useful life of your cylinder coating can be gone in a few seconds of 'light' honing. I reckon the 'grand canyon' on ring end gaps makes those bore scratches pretty insignificant in comparison.

I'm wary of the 'H' word and would suggest anyone considering it should very accurately measure their cylinder first - quite a tricky thing to do in itself, even with the best instruments. Need to also be mindful that cylinders don't wear evenly, especially a 2 stroke down at port height due to much less bore material.

I especially don't like the idea of ball/grape or flapper type hones as it seems to me you risk damaging the coating on the port edges.
I've never seen one of these expensive diamond hone machines but I think you're dealing with a very different animal there. I'd say a great deal of accuracy could be had with one of these and you're likely to end up with a better surface as well. Don't quote me (and buggered if I know if it even matters much) but I seem to recall reading that other type hones can tend to gall up (microscopically) the bore surface somewhat. An oil molecule might appreciate the difference?

As far as using a scotchbrite pad goes, I was initially very hesitant with it but it worked well. My bore was pretty grubby and I'd much rather remove any glaze by hand than with any type of hone. It's slow but you can see exactly what you're doing. Light pressure and some CRC is all that's needed to break up the glaze. Once through that I finished with paper towels and turps until spotless.

Pays to check even brand new parts alright tommorth. I checked ring lands etc for edge dings and slightly relieved the very sharp edges on new piston. Found a nasty little ding on skirt edge and gave it some extra attention. I even cleaned the new wrist pin bearing even though it came pre-oiled in sealed plastic. Bunch of tiny shinies came off it. Factories/machine shops are not clean places.

As said earlier Reckless and yourself have valid points and I'm in full agreement about the complexity (spelling) of honing. My point is if you are going to get it done then make sure it is done properly. This is also why I have suggested Engine Specialists who use diamond precision type hones, not the standard of the mill ones that the average joe blow mechanic as. As for taking out scratches with a hone I think you have missed the point. I'm not talking about taking out deep scratches, just the light scratches which your scotch brite will take off. As for a scotch brite I'm not keen on using them. The average bloke who does his own top end may not be the best suited to use this method; as you still take off some of the nicasil you have to make sure you do it evenly, all around otherwise you can end up with an uneven surface...

Each to there own though...

[Reckless]

Yeh Spelling not my best thing! Thank goodness Google toolbar has a spellchecker!!

Secondly I don't think any of us are saying your wrong littlejohn according to some articles I have read you are quite right! But personally I still don't see the point in wearing a nikasil bore more than necessary. I am also just a bit scared of the horror stories I have heard about honing and the nikasil re-plating process. So best off not do it and put up with a not so perfect bore that hopefully the 2 stroke oil & ring-seal will compensate for. Bearing in mind nearly everything I have read and found on the dyno-More oil equals more horse power. Most karters where running 20:1 in my day and I discovered here that the Road race boys have found the same with there high performance 2 smokers. Oh well enough said we'll start chasing our tails soon LOL!!!!

Thirdly the reason for my post. I don't think you need to worry to much Cham about the 'Grand Canyon" called the ring end gap! Its the only bit of steel stuff (chrome molly?) in there and being thin I would expect it expands the most of any part under heat and the gap is minuscule when the engine is hot. Which of coarse is why we have to check it each time to make sure there is enough gap so the ring ends don't touch and cause a seize. A lot of people don't know to do this of coarse. Very seldom do you have to address this issue but the one you don't check always bites you!!

[camchain]

No sweat LittleJohn. I wasn't offended in any way by your view on the scotchbrite pad. It's a valid warning (It is an abrasive so potential for damage is there). Hope the reverse applies - wasn't having a dig at you, was more IMO-ing generally about principles being discussed. Getting different views on things is a very healthy thing and I like it - otherwise I'd just sit around agreeing with myself!

The devil is in the details with this stuff. For the time being at least, I'll stick with my 'no honing' preference for removing any glaze. I see the 'advantage' of uniformity of a mechanical hone as potentially a problem with removing any glaze because glaze is unevenly distributed on the bore surface. Even though glaze is softer and will come off quicker, The hone will still be doing its thing on glazed and unglazed sections alike so the operation will be inherently uneven.
Maybe a mild acid (muriatic?) would be the best way to remove any glaze? I did consider using caustic soda (not acid but alkaline) as it does such a good job on expansion chamber carbon but it's fierce stuff and I thought a bit risky to even test it.

I wish my bore still had ALL of the scratches it had prior to honing lol! I do still like the idea of a nicely honed bore surface and max oil retention but I'll be very gun-shy of going after it from now on. Even experts can make mistakes, especially where margin for error is so small.

I always find Reckless's info from his karting background interesting so along those lines here's something on the principle of surface 'texture' for lubrication. Basic principle works even on very large scale. I did my apprenticeship with NZ Electricity. Power station generator shaft bearings are massive white metal jobs. Thrust bearings are made in sections like slices of a huge cut up pie. They would be milled flat but finished by hand. Using scrapers we would cut shallow little oil retention pockets evenly all over bearing surface.

BTW top end assembly trick: Before re-fitting cylinder over (2 stroke) piston/rings I put felt pen lines on piston to mark position of ring locator pins. Makes it a bit easier spot where pins are when squeezing rings up while doing a 3 handed job with 2 hands.

Reckless, I started a thread out in the engine section hoping to find out more on all what all these clearances might be with engine at operating temp but didn't really get a definitive answer. Forgot to try ring end gap with my 'oven bake test'. Thanks for reminding, will have a play next top end job.

[LittleJohn]

BTW top end assembly trick: Before re-fitting cylinder over (2 stroke) piston/rings I put felt pen lines on piston to mark position of ring locator pins. Makes it a bit easier spot where pins are when squeezing rings up while doing a 3 handed job with 2 hands.

No worries camchain, am also always interested in how others do things, is the best way to learn...

Good tip about the pen, I always keep some masking tape and a pen handy when stripping bikes. Especially if they are going to be apart for a while when waiting on parts. Also use ice-cream containers to seperate all the sections of parts.

[cheese]

No worries camchain, am also always interested in how others do things, is the best way to learn...

Good tip about the pen, I always keep some masking tape and a pen handy when stripping bikes. Especially if they are going to be apart for a while when waiting on parts. Also use ice-cream containers to seperate all the sections of parts.

Thats cause masking tape is what holds the Navy together!

[LittleJohn]

Thats cause masking tape is what holds the Navy together!

Now you are showing your age, maybe you should be known as oldskool2....

These newskool days they use bungy cord and velcro (allows ice strengthing to be maintained)

[Reckless]

Reckless, I started a thread out in the engine section hoping to find out more on all what all these clearances might be with engine at operating temp but didn't really get a definitive answer.

Don't think many/any would know definitively Cham only the factory probably.

Forgot to try ring end gap with my 'oven bake test'. Thanks for reminding, will have a play next top end job.

You put your piston in the oven to measure the tolerances heated? Your a kean man that's for sure!
Now that's not a go at you because we used to make special cover plates for the exhaust and inlet. The inlet one had a fitting on, that our POP off gauges fitted onto and we would pump the engine up with a few PSI then put them into hot/boiling water to simulate running temperature. If we saw any bubbles coming out of the crankcase seals, base gasket or anywhere that meant any loss of pressure up the transfer ports etc it meant we where loosing that valued pressure, which meant another strip down to fix it. Now don't have a go at me for being over the top, they were race engines and a 10th gained on the track was alot!! I mean if you go to the trouble of line boring, trueing and balancing the crank, matching and polishing the transfers why not ensure you have no leaks? Pretty simple really!

[camchain]

I'm a big fan of working methodically too. Clean parts, threads on screws etc. bits in containers relative to assembly etc. If doing a potentially tricky job on new bike I also like to lay parts in a line in correct order. Foolproof when going back together.

Reckless did you find air leaks on kart engines very often with that method? I'm a bit suspicious of my base gasket near the back. Had silicone there when removed but only at rear, and noticed even brand new KTMs have silicon bead at rear of cyl (near reed block).

Yeah - Oven test was also to try and get a better idea of what was happening as engine goes from cold to hot. Judging by rapid expansion of piston skirt I'll now be a bit more careful until engine at full temp. I used to think lots of wear at moment of startup, getting safer as time went on. Now believe probably the real risk point is maybe 2 or 4 minutes after start - when rapidly expanding piston is getting tight against slowly warming cylinder (especially with water cooling).

Jeez I'm a shocker for thread bloat. We'll be talking about running in after rebuilds next.

Edit: Might look into getting some of this Navy tape - sounds good for leaks.

[Reckless]

Reckless did you find air leaks on kart engines very often with that method? I'm a bit suspicious of my base gasket near the back. Had silicone there when removed but only at rear, and noticed even brand new KTMs have silicon bead at rear of cyl (near reed block).

We actually used to put silicon on the base gasket as we had the barrels of so many times we didn't want to have to buy new base gaskets each time. Only a very very thin smear of coarse didn't want it to bleed trough on the edges and interfere with the transfer port channels.

We found very few air leaks on a reassembled motor, where mainly checking the big end bearing seals actually, but we where very fussy about the way they went back together. More found on my sons Racket 85 Cadet Kart after it had done a few meetings. But the tech's used to strip those often to make sure they where legal so they where apart quite frequently, easy enough though no gearbox. These where the main engines we mostly used the water test on as well!

Jeez I'm a shocker for thread bloat. We'll be talking about running in after rebuilds next..

No thread bloat there mate! Running in is easy!!!
Only start it after a re-ring or piston in the garage long enough to make sure it will actually go when you take it to a ride, say 5-10secs, They say you shouldn't do this but I'm not drving all the way to Mercer not knowing if it will even go!!
Take it to the ride, Warm it up well, ride it!!! (not thrash it, but ride it well).
Hint: Main thing is to load it on acceleration and deceleration no constant throttle.
Done!

Actually I always warm up well!! Always!

details here http://www.mototuneusa.com/break_in_secrets.htm Disregard the four stroke stuff though!

Worked for me everytime! Even before I found Mototune I did it accidently out of impatiance. I could only ever do 20 laps at average speed before I found I was caning it! Always had fast engines, good ring seal, no blow by!!

[LittleJohn]

I'm a big fan of working methodically too. Clean parts, threads on screws etc. bits in containers relative to assembly etc. If doing a potentially tricky job on new bike I also like to lay parts in a line in correct order. Foolproof when going back together.

I like to use an egg carton to seperate parts into order, especially good for taking the gears and other associated shafts apart.