THE WORKSHOP MESSED UP! 😒 | 1973 Kawasaki S2A Engine Repair - Pt3

The cylinder 1 barrel of my S2A gets re-bored, but the piston clearance is still out of tolerance!
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[@UOO303T]

I think you have done a excellent job Derek

[@derekb2765]

Thank you. Nice of you to say 😌 The work's not over yet, as I want to sort the other two cylinders too. 🔧

[@michaelfirth1075]

I had an 72 s1 back in the day, they all rattled natural sound for them . Great bike , great video.😊

[@derekb2765]

A few people have said that lol 😂 Glad you enjoyed the video 👍

[@johnc9187]

This just came into my KZbin feed. Really interesting and brilliant way of loading the pistons into the barrel before putting in the gudgeon pin in. All my bikes were two strokes from my Moped in 1978 to my 500H1F and always put the poison onto the con rod first before lowering the barrel. I will give your method a try next time 👍. I have been lusting after another 400 but might just go for a 350, never had one before. Enjoy your bike, there is nothing better than and accelerating two stroke triple 😂

[@derekb2765]

Glad you enjoyed the video! 👍 Yes, loading the piston into the barrel first certainly makes the job a whole lot easier 😀

[@UOO303T]

You obviously know yr onions mate well done

[@derekb2765]

Thanks mate. Fortunately there's a lot of information out there, namely in KZbin videos, Kawasaki forums and knowledgeable viewers. 👍

[@ihateemael]

compression tests on 2 strokes is a bit hit and miss. Best bet is to strip and measure. Chances are bores will be oval, worn around exhaust port. Two strokes run best with tight clearances, like the shop did for you. Though the runin process can be arduous. Some bedin successfully quite quickly, others sieze at the drop of a hat. If you still have the oil pump, bleed the lines and use an expensive syn oil. Also add a capful to the tank at fillup. Check the carb jets with book, consider lowering needle clip x1? depending on how it runs. Stock air cleaner stops off idle spit. Those triples smoked a lot around town, were good at the track. Balance carbs and most important check ignition timing! All the best, cheers.

[@derekb2765]

Thanks for the tips. Cheers! 👍

[@markdavies5508]

Loved the out-take at the end. Enjoying your journey getting the Kawa going - thanks.

[@derekb2765]

Glad you enjoyed the video 👍

[@alistairshaw3206]

Here's hoping the Kawasaki will be back at its best! I've sent two barrels for my DT3 to a place in Wolverhampton to bore the best one and supply a matching piston. Hopefully, I will get word soon.

[@derekb2765]

Best of luck with your job too! 🤞 Do you mind me asking how much you're paying for the rebore? 🤔

[@alistairshaw3206]

@derekb2765 I'm not sure at the moment, I'm waiting for them to get back to me with a price. I'll let you know when I find out.

[@derekb2765]

Cheers 👍

[@f4rexk163]

Keep up the videos! love your attention to detail and how you explain everything 👍

[@derekb2765]

Thank you for the kind words ☺️

[@paulsilson2148]

Seems like your a man of knowledge Derek. Well done.

[@derekb2765]

Thank you. Most of what I've learned has been through trial and error. Plus there's so much information out there to help DIY enthusiasts! 😀

[@rangie944]

Thanks for the update Derek, those triples old but still great.

[@derekb2765]

Cheers mate. Thanks for watching 👍🏿

[@Rollie961]

Nice one Derek great idea for checking the tolerance on the cylinder 👍

[@derekb2765]

Cheers mate. I've learnt that you can't take any chances w.r.t. certain critical tolerances ☝🏿

[@davidyendoll5903]

Nice . Ring ding ding , cough ! Lol , love to see you and my mates GT550 at Hyde Park corner !

[@derekb2765]

Thanks mate. Is Hyde Park Corner the site of a regular classic bike meet? 🤔

[@charliestoybox2099]

Nice attention to detail. Hope she runs great.

[@derekb2765]

Thanks mate. It's not running so great, but due to another issue that I'll cover in a subsequent video! 😯

[@mozer30]

What concerned me looking at your cylinder is the lack of port chamfer. (Or what little I can see) As you’ve had the bore increased by 0.5mm it’s likely that the old port chamfering has been removed. They should have been redone after the rebore, but is often missed if auto engineer company are not familiar with 2 stroke cylinders. Port chamfer is done to eliminate the chance of ring snag when it passes over the port windows, especially the wide exhaust port.

[@derekb2765]

I did check that, and lightly chamfered the edge just to make sure. 👍

[@grahamsmith8122]

You might be able to buy a second hand boring machine Derek? I used to do loads of rebores, back in the day but very few people do nowadays. Sadly those that do can sometimes do it wrong!

[@derekb2765]

Unfortunately I don't have the room for such heavy duty machinery. I'd love to have a proper engineering workshop a la Allen Millyard 🤢

[@hughhennessy2664]

Try some PTFE tape on the connecting treads, if the pressure loss is from there it will seal it. Beautiful bike!

[@derekb2765]

I tried that on the adapter thread, made no difference. Too risky to try on the spark plug thread 😯 Glad you like the bike. Thanks for watching 👍🏿

[@derekb2765]

Rubber mounting the motor significantly reduced the vibration I presume? H2s certainly are vibey bikes! 🫨 It's a shame that it's demise wasn't more...grandiose 😉

[@mototoki]

Really nice video Derek. Everything done perfectly. You might want to try a leak down test before you get out on the road just to check you don't have any air leaks that'd cause a lean condition and mess up all your work!

[@derekb2765]

Glad you enjoyed the video. Thanks for the tip! 👍 But do I need to do leak down testing, since I've already established good compression? 🤔

[@mototoki]

@@derekb2765 The compression is just piston rings & head gaskets, the leak down is base gaskets, inlet stubs, cranks seals. Poor compression just means poor power, air leaks can mean a seize. I do wonder how you picked up the damage in the first place, it *could* be air leaks. I have a vid on this, but happy to catch up offline if you want a chat 👍

[@derekb2765]

Ok, I'll have a look at your video. Thanks for the heads up 👍

[@mototoki]

@@derekb2765 No worries, if you need anything, give me a shout ☺

[@derekb2765]

👍

[@vwpieces]

Good catch on the bore size. Hone looked coarser than I like, Some 2000 wet by hand would have helped. But 125psi in that condition is fine.

[@derekb2765]

Yeah, that compression cold is ok. And consistent across cyls. I'm wondering if I should use another workshop for boring the other 2 cyls though 🤔

[@vwpieces]

@@derekb2765 I took my cylinder for my 1963 Honda CB77 to a well known local guy. One man shop, took over 3 months till he had enough small cyls to do a setup run. I replaced the sleeves myself, he did bore on 2 cyls and also decked the top. Well worth the wait, wish I could share a pic. Just made an adapter for the M12 to fit my compression tester, just checked yesterday, 155 and 157#. I did the build and head work myself.

[@vwpieces]

@@derekb2765 Also, 12yrs ago when I first finished the H1, I had the center cyl seize late in the riding season. Life got in the way and didn't get it back together till this past winter. OOOH, what I have missed riding it. Turns out I didn't use any sealer on the cyl base gaskets. Found an imperfection in the cyl base casting... air leak!. They all got sealer this time.

[@derekb2765]

I presume you have some heavy duty workshop machinery. I'd love to have that a la Allen Millyard, but I don't have the space 😢

[@derekb2765]

That's interesting. One of the viewers of my latest video was recommending that I leak down test any newly rebuilt cylinders. I'm going to do it when I get around to reboring the remaining 2 cyls of my Kawasaki 👍

[@BRaff-hl4ip]

I'd imagine the rubber tubing would expand slightly, thus affecting your compression test reading.

[@derekb2765]

That would just mean that I'd have to pump longer until the tube expands. But the pressure remains consistently low regardless 😬

[@eamonnquinn9585]

To my mind it’s ok to have the rubber hose you got to check all three with the same set up. Hope the run in goes well :-) love the bike

[@derekb2765]

A viewer has a Draper compression test kit that measures accurately with the lead. I need to source one, so I can measure across all cylinders 🤔 Glad you like the bike. Thanks for watching 👍🏿

[@stuartpage4100]

I have the same compression tester, mine works fine, i get 140psi on all 3 cylinders on a GT380. are you missing the O ring on the end that screws in the cylinder.

[@derekb2765]

I've tried with and without O rings, adaptor thread with PTFE tape, etc. Made no difference 🤔 Another viewer experienced the same issue, and bought a Draper test tool instead. I'll probably get one too! 👍

[@lucybrown-nd1cf]

yes to rubbish chinese compression tester, mine indicated 50 psi when it was 130, chucked it in the bin and got a draper one.

[@derekb2765]

Draper eh? Ok, I'll check that out. Thanks for the tip! 👍

[@dogpaw775]

i'd of rebored all cyl's to alay problems down the line and for future owners, ease up on over oiling the bore on assembly otherwise rings won't bed in correctly and the bore will glaze, copper doesn't need to be annealed in water and even if done to speed things along plastic and glass containers are probably not the best for hot items, clean the rough oxide off to aid better sealing. That pressure testing gauge appeared to be flexing alarmingly at the plug end. i'd persevere with the flexible couple and 'massage' the threads to seal . otherwise all good and looking forward to the ring dinga ding ding ding start up.

[@derekb2765]

Cheers for the tips. ☺️ Thanks for watching 👍🏿

[@cabovermike]

Should there be an O ring in that head recess ?

[@derekb2765]

No. I even referred to the parts diagram to double check 👍

[@bananabrooks3836]

Did the workshop have the new piston and did you provide full clearance details to them? A shop with any nous would have requested these anyway.

[@derekb2765]

I supplied the new piston and clearance specs 👍 In the Pt2 video (A Second Opinion), the engineer tells me what I need to provide to him.

[@bananabrooks3836]

@@derekb2765 Yes l saw that, what are THEY measuring with, tailors tape?!

[@derekb2765]

That's why I performed the double check before starting the rebuild. Quality workmanship isn't a given nowadays 😕

[@zaks9919]

I presume you did a ring end gap ?🤔

[@derekb2765]

I didn't check the ring end gap of the new piston, because the rings were already fitted to the piston, and I didn't want to risk stressing them by the removal and refitting. 👍

[@pbysome]

G udgeon pin not cudgeon, cant rebore one cylinder mate engine will vibrate, rebore all or resleeve the one and it isnt about compression.

[@derekb2765]

According to a couple of engine specialists that I consulted, going 0.5mm oversized on one piston makes negligible difference to the engine balance. One of the discussions is in the Pt2 video (A Second Opinion). I intend to rebore the other two cylinders anyway, as they're rattly.

[@pbysome]

@@derekb2765 been building engines for best part of 40 years and I would only ever do that if I was skint and needed the ride. Why bother balancing crankshafts if you ignore the weight difference of a size up in piston size? Not to mention the better seal on the bore the whole plot is out of balance, sure it'll run and if that is all you are concerned about then go at it.

[@derekb2765]

As I said before, I will get the other two cylinders rebored, as I want to get the engine running optimally. 👍

[@stephenhepburn6374]

half mm bigger piston on one cylinder ,you now got an unbalanced crankshaft,should really rebore all 3 Derek

[@derekb2765]

I got a few opinions from engineers, who said that 0.5mm difference on one won't make any difference to the balance. The Pt2 video (A Second Opinion) shows one of these discussions 👍

[@stephenhepburn6374]

@@derekb2765 It will run ok,but if you ride the bike lots worth doing other 2 ,those bikes deserve the effort, keep it up.

[@derekb2765]

At the end of the vid, I mention that I'll eventually do the other two, as they're rattly. Probably due to worn out barrels 👍

[@markpavletich747]

My H2 actually ran smoother with just the left hand cylinder bored .5mm oversize.

[@derekb2765]

Sounds like you solved some performance issue with the rebore 👍