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Post by tony2stroke on Jun 9, 2020 21:36:28 GMT 1
one other thing, if it was down to swarf left in ports, I would be worried about the crank bearings too, sorry to worry you.
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Post by bid on Jun 9, 2020 21:54:25 GMT 1
Ohh i hope not,
but i know what your saying, i must say, the crank does look very clean with no bits or swarf on it or shiny particals, i'll fill the crank with some petrol and spin the crank and then syringe it all out to see if its clear of bits, 🤞
Dave
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Post by tony2stroke on Jun 9, 2020 22:11:53 GMT 1
Ohh i hope not, but i know what your saying, i must say, the crank does look very clean with no bits or swarf on it or shiny particals, i'll fill the crank with some petrol and spin the crank and then syringe it all out to see if its clear of bits, 🤞 Dave I hope not too for you! I agree that crank looks clean and not all stained with blow by or use, I know its a pain, if there is swarf in there it will sink to the bottom when you clean it, you could try filling case with fuel and turning engine over a bit, then use one of those little magnet tools for fishing metal things out of the engine that get dropped in by accident, that would show you any swarf on the end of the magnet. You may need to take the engine out and tip upside down to clean it out, and then keep your fingers crossed none stuck to the bearings. Better to be armed with all the info you can be, even if its not good news. |
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Post by bid on Jun 9, 2020 22:18:36 GMT 1
Good call, ive got one of those magnet tools, i'll get that done tomorrow, then maybe i'll be able to sleep soundly, or that will be going to pjme too, even though thats just been rebuilt too, wish me luck, 🤞
Cheers
Dave
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Post by tony2stroke on Jun 9, 2020 22:23:53 GMT 1
Good call, ive got one of those magnet tools, i'll get that done tomorrow, then maybe i'll be able to sleep soundly, or that will be going to pjme too, even though thats just been rebuilt too, wish me luck, 🤞 Cheers Dave I certainly wish you all the best mate, just worth checking to be sure, you don't want or need any more trouble. |
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Post by bid on Jun 9, 2020 22:28:04 GMT 1
Your not wrong there,
Thanks mate
I'll let you know how i get on tomorrow,
Cheers
Dave
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Post by JonW on Jun 10, 2020 2:55:16 GMT 1
It would appear that Mitaka buy whatever they can get hence why some boxes say made in Japan and some say made in Taiwan Maybe during this covid crap supply chain nightmare they have sourced pistons from TKR Rather worryingly to us all the Mitaka makes this attached statement on their website 🤔 Steve Over the years Mitaka and TKR have often been linked and talked of as the same pistons, it is my experience that if you get a box of mitakas that say Japan on them, then they are the TKR(J) ones. Ive also found that so long as you get the Japanese ones then you are golden... BUT, if you get the Taiwan ones then send them back right away and do some more shopping. FWIW It clearly states their origin on the box, so only buy if they say Japan. The others are just junk. Badly cast and poorly finished. I have photos of a set here if anyone wants to see, or just buy your own lol. Sadly, Ive seen plenty of builds (usually on Fb actually) where guys proudly show off the parts theyve been sent for the top end rebuild, claiming they did good and got sexy Mitaka pistons. However you can see on the boxes where they come from so Im always shocked when guys then happily build their bikes up with the junk theyve been sent. Maybe they dont know a good piston from a crappy one, which is a fair point if its your first go at this I guess. As an aside, some of the poor casting was actually divots and voids in the piston crown, not at all ideal for safe running... but will also have the next owner chasing their tail wondering when and where the 'bits that burnt/broke off' went thru their engine at the next bit of maintenance. I say that as most of the builders who seem to use these pistons are those who sell their bikes on. Go figure. Bizarrely the CruzinImage pistons which are also I believe from Taiwan are much better made and even got the nod from my reborer (he laughed like I did at the Taiwan mitakas). To avoid any issue, just buy the ones in the boxes that say TKR and Japan. The pistons in those boxes look like pure CNC vs the "workmanship" (like the same 5 year old who previously used to work for Raask went to work there) of the casting on the Taiwan mitaka junkers. Anyway... youve defo found the issue with the performance on your bike bid. Good work. |
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Post by dusty350 on Jun 10, 2020 7:11:18 GMT 1
If you run on a Castor based oil and then change to a non Castor oil, you can get gumming problems as the oils react to each other. The engine needs cleaning of any Castor reside before using new oil. My 400e was a race school bike originally, and ran on Castrol R. I got a bike shop to properly clean all the Castor residue out of it before I used a different oil - shame it blew up less than a week later, but that's another story ! Dusty  |
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Post by oldbritguy on Jun 10, 2020 7:49:12 GMT 1
I have just got my cylinders back from PJME with new liners fitted. Absolutely top job. First thing I looked at was "were the pistons marked L + R and matched to the bore" . Yes they were . Known brand? Mitaka, check. Next was country of origin on the box - "made in Japan" so I am happy I know where the box came from and at least expect the pistons inside to be good quality too. Particularly after following the theme of this thread. You can be unlucky pick up a dodgy batch of pistons or any engine components for that matter especially aftermarket products but it is good to know some manufacturers have a better rep than others. Finally the reputation and skill of the engineer doing your work is key to getting a good job done. The best engineer on old and basic equipment fitting top parts will do a better job than a poor engineer on the best modern equipment. Reputation and word of mouth backed up with the goods should help us choose who gets our business and who does not. That is what this great forum is all about, sharing that info and experience. John  |
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Post by bid on Jun 10, 2020 10:01:37 GMT 1
Great info guys
Cheers
Dave
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Post by tony2stroke on Jun 10, 2020 10:26:54 GMT 1
It would appear that Mitaka buy whatever they can get hence why some boxes say made in Japan and some say made in Taiwan Maybe during this covid crap supply chain nightmare they have sourced pistons from TKR Rather worryingly to us all the Mitaka makes this attached statement on their website 🤔 Steve Over the years Mitaka and TKR have often been linked and talked of as the same pistons, it is my experience that if you get a box of mitakas that say Japan on them, then they are the TKR(J) ones. Ive also found that so long as you get the Japanese ones then you are golden... BUT, if you get the Taiwan ones then send them back right away and do some more shopping. FWIW It clearly states their origin on the box, so only buy if they say Japan. The others are just junk. Badly cast and poorly finished. I have photos of a set here if anyone wants to see, or just buy your own lol. Sadly, Ive seen plenty of builds (usually on Fb actually) where guys proudly show off the parts theyve been sent for the top end rebuild, claiming they did good and got sexy Mitaka pistons. However you can see on the boxes where they come from so Im always shocked when guys then happily build their bikes up with the junk theyve been sent. Maybe they dont know a good piston from a crappy one, which is a fair point if its your first go at this I guess. As an aside, some of the poor casting was actually divots and voids in the piston crown, not at all ideal for safe running... but will also have the next owner chasing their tail wondering when and where the 'bits that burnt/broke off' went thru their engine at the next bit of maintenance. I say that as most of the builders who seem to use these pistons are those who sell their bikes on. Go figure. Bizarrely the CruzinImage pistons which are also I believe from Taiwan are much better made and even got the nod from my reborer (he laughed like I did at the Taiwan mitakas). To avoid any issue, just buy the ones in the boxes that say TKR and Japan. The pistons in those boxes look like pure CNC vs the "workmanship" (like the same 5 year old who previously used to work for Raask went to work there) of the casting on the Taiwan mitaka junkers. Anyway... youve defo found the issue with the performance on your bike bid. Good work. Looks like Mitaka pistons reputation has just gone down the pan. Lots of people working on these bikes these days just don't have a clue, lots of info has been lost in the mists of time and only available on sites like this, or a very few old school places and one man bands. Most bike and car so called mechanics these days are not mechanics, they are just fitters, with little idea, they just fit new parts the computer told then to, and they don't even know a good part from a bad part. We all know fb is full of numptys without a clue about anything, look at my wonderful thing, but unfortunately its not wonderful, but a pile of **** Personally I would rather pay more and get it right in the first place, this is why I always look for genuine parts that matter. I am quite happy to buy lots of cheap unimportant bits and fettle them myself, but some bits you just shouldn't take the risk, it only costs you more in the end. |
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Post by Gitram on Jun 10, 2020 11:33:35 GMT 1
I got my hands on a set of 375 barrels and taiwanese pistons fresh out of the box and popped it all onto my 250..(plus a set of 350 carbs) holy toot, what a difference.. after about ten miles one of the pistons broke up. now if i had been thrashing it I would have thought i was being a bit rough but i hadn't gone above 6000 revs apart from a slight jerk of the wrist when i went over a humpback bridge, anyway, one rebore with jap pistons and a crank build later plus the purchase of a stepthrough to get into work.. it was good for several thousand miles.
There may have been several factors which contributed to the catastrophic failure but the thing i remember most was that the new pistons were nice and shiny compared to the duller finish of the first set
marti
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Post by tony2stroke on Jun 10, 2020 11:39:59 GMT 1
I got my hands on a set of 375 barrels and taiwanese pistons fresh out of the box and popped it all onto my 250..(plus a set of 350 carbs) holy toot, what a difference.. after about ten miles one of the pistons broke up. now if i had been thrashing it I would have thought i was being a bit rough but i hadn't gone above 6000 revs apart from a slight jerk of the wrist when i went over a humpback bridge, anyway, one rebore with jap pistons and a crank build later plus the purchase of a stepthrough to get into work.. it was good for several thousand miles. There may have been several factors which contributed to the catastrophic failure but the thing i remember most was that the new pistons were nice and shiny compared to the duller finish of the first set marti Lesson learned!!!!! |
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Post by chrisg on Jun 10, 2020 12:41:26 GMT 1
I have just got my cylinders back from PJME with new liners fitted. Absolutely top job. First thing I looked at was "were the pistons marked L + R and matched to the bore" . Yes they were . Known brand? Mitaka, check. Next was country of origin on the box - "made in Japan" so I am happy I know where the box came from and at least expect the pistons inside to be good quality too. Particularly after following the theme of this thread. You can be unlucky pick up a dodgy batch of pistons or any engine components for that matter especially aftermarket products but it is good to know some manufacturers have a better rep than others. Finally the reputation and skill of the engineer doing your work is key to getting a good job done. The best engineer on old and basic equipment fitting top parts will do a better job than a poor engineer on the best modern equipment. Reputation and word of mouth backed up with the goods should help us choose who gets our business and who does not. That is what this great forum is all about, sharing that info and experience. John Are they the PV pistons? is it for a PV bike? |
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Post by oldbritguy on Jun 10, 2020 14:32:52 GMT 1
Hi Chris
No. LC pistons (4LO) in LC cylinders which are different from PV pistons.
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Post by tsa on Jun 10, 2020 15:32:32 GMT 1
Hi steve, Ive a feeling you could be right, The rings have a lot of sticky burnt oil on them as you can see in the pic with the ring in the cylinder, It proberbly didnt help running it in with silkolene pro kr2 castor blend🤔 Then when i fitted the pump off arrow i changed to motul 710, Dave  There is another issue right here. Castor oils do not mix with synthetic oils at all and makes sticky mess inside. The guy who did the rebore I guess was wearing spurs and a stetson. Can you see the honing marks as with only 600 miles on it they should be very easy to see and maybe feel. Is there a lip near the top of the bore where the rings stop at TDC. If it has it wasnt rebored. |
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Post by arrow on Jun 10, 2020 17:08:02 GMT 1
Other than being a fantastic lubricant in highly stressed racing engines that are split regularly, Castor is bad news in our road bikes. This is a pump I sorted 4 years ago that was running Castor. Most of the steel parts were scrap, due to severe corrosion.  |
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Post by chrisg on Jun 10, 2020 18:42:56 GMT 1
Hi Chris No. LC pistons (4LO) in LC cylinders which are different from PV pistons. I know, but a lot of re-bore companies will fit PV piston as a matter of course. Grampian being one of them. |
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Post by bid on Jun 10, 2020 19:51:23 GMT 1
Hi steve, Ive a feeling you could be right, The rings have a lot of sticky burnt oil on them as you can see in the pic with the ring in the cylinder, It proberbly didnt help running it in with silkolene pro kr2 castor blend🤔 Then when i fitted the pump off arrow i changed to motul 710, Dave There is another issue right here. Castor oils do not mix with synthetic oils at all and makes sticky mess inside. The guy who did the rebore I guess was wearing spurs and a stetson. Can you see the honing marks as with only 600 miles on it they should be very easy to see and maybe feel. Is there a lip near the top of the bore where the rings stop at TDC. If it has it wasnt rebored. Hi tsa, There is hone marks at the sides of the cylinder but not so much at the rear and front of the cylinder they have worn super shiny for some reason, it was rebored though as the old size was 1.25 with ypvs pistons, theres no lip near the top thats fine, Cheers Dave |
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Post by zig on Jun 10, 2020 19:53:29 GMT 1
Yeah it aint good, i'm still going to send the cylinders to pjme, to see if they've been over bored, if there ok i'll get some new rings, as steve said there gummed up and proberbly worn with swarf, its a shame if it needs a rebore because its just been done to 1.50 a wasted rebore, 🤞 Dave send the lot to PJME and forget about it for 2/3 weeks and when you get it returned and fitted you will have peace of mind knowing it was done true and properly + supplied with the right pistons & rings etc it's what I did with my PV barrels which I got back 2 weeks ago and I know in my mind the work was carried out professionally and will never need looked at again , run on the proper 2stroke oil of course and all that ZiG |
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Post by bid on Jun 10, 2020 19:59:49 GMT 1
The crank is swarf free, 🙏 I filled the crank with fresh petrol and spun it round and used a magnet tool down there, and no swarf, then used a syringe and tube to suck all the fuel out it was just a little dark coloured with zero particals or bits, phew, so it didnt wear the rings with swarf, just over bored it too much What a relief🍻 Dave    |
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Post by jon on Jun 10, 2020 20:23:42 GMT 1
Just a bit of advice.
Get some fresh 2T oil over those big ends ASAP.
Jon
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Post by midlifecrisisrd on Jun 10, 2020 21:12:48 GMT 1
What Jon says
Get your syringe filled with 2 stroke oil and lube the 2 big ends then put some down each hole to feed the main bearings with oil before spinning the crank a bit
Steve
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Post by bid on Jun 10, 2020 21:16:57 GMT 1
Yeah it aint good, i'm still going to send the cylinders to pjme, to see if they've been over bored, if there ok i'll get some new rings, as steve said there gummed up and proberbly worn with swarf, its a shame if it needs a rebore because its just been done to 1.50 a wasted rebore, 🤞 Dave send the lot to PJME and forget about it for 2/3 weeks and when you get it returned and fitted you will have peace of mind knowing it was done true and properly + supplied with the right pistons & rings etc it's what I did with my PV barrels which I got back 2 weeks ago and I know in my mind the work was carried out professionally and will never need looked at again , run on the proper 2stroke oil of course and all that ZiG Hi Zig, Absolutally, there going to pjme next week😀 Dave |
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Post by jon on Jun 10, 2020 21:18:34 GMT 1
In fact it might even be better to mix a very high percentage of 2T oil with petrol and repeat the process so the main bearings are coated with 2T oil too.
Or do as Steve suggests, but I wonder how well this will be distributed. If you think how they are normally lubricated.
Flash rust can form very quickly.
Jon
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Post by bid on Jun 10, 2020 21:40:12 GMT 1
In fact it might even be better to mix a very high percentage of 2T oil with petrol and repeat the process so the main bearings are coated with 2T oil too. Or do as Steve suggests, but I wonder how well this will be distributed. If you think how they are normally lubricated. Flash rust can form very quickly. Jon Good point, I,ll nip in there and do it now just incase the 2t lube aint enough, Cheers guys, Dave😉 |
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coose
Drag-strip hero
Posts: 270 
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Post by coose on Jun 11, 2020 9:32:32 GMT 1
Other than being a fantastic lubricant in highly stressed racing engines that are split regularly, Castor is bad news in our road bikes. This is a pump I sorted 4 years ago that was running Castor. Most of the steel parts were scrap, due to severe corrosion. It's such a shame that nobody ever listens.....  |
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Post by JonW on Jun 11, 2020 14:06:16 GMT 1
I never understand when people talk about using that stuff. Some say 'i just put a capful in every tank of fuel as it smells so nice'... Nah I dont really get it, if the bike worked better with it in there then we'd all be doing it. lol
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Post by bare on Jun 11, 2020 20:56:45 GMT 1
Wouldn't get overly excited re End Gaps.
OEM Yama rings were almost Never even close to their specs. Wayyy to big a gap.
Yet Yama rings are /were best made.
No idea about some jobber rings from wherever tho.
From pix your cyl sleeves look a fair bit thinner than Oem ..so who knows how many rebores remain.
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Post by bid on Jul 18, 2020 19:46:28 GMT 1
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