|
Post by bid on Jun 9, 2020 17:09:41 GMT 1
Hi Guys, I think ive finally found out why the power at the top end is lame, after pulling my hair out and wasting loads of cash chasing this problem, never let anyone else build your engine, and mostly use a reputable company to do your rebores, the guy who rebuilt my engine must have never checked the rebore work he had done. I saw the problem when i took the exhaust of the other day, and saw loads of blow by past the rings, so i thought i'd investigate, this is just 600miles since rebuild😤
|
|
|
Post by tony2stroke on Jun 9, 2020 17:16:27 GMT 1
O M G!!!!!!!!!! that is a lot of blow by for a supposed thresh re-bore after 600 miles, must have sounded like a bag of spanners clattering around.
|
|
|
Post by bid on Jun 9, 2020 17:17:14 GMT 1
The ring gap is way out at 0.53mm supposed to be 0.30, lesson learnt😭 Also the ports have been raised 2mm will these be ok and not too peaky when i get pjme to do the rebore? Thanks guys😉
|
|
|
Post by bid on Jun 9, 2020 17:22:41 GMT 1
O M G!!!!!!!!!! that is a lot of blow by for a supposed thresh re-bore after 600 miles, must have sounded like a bag of spanners clattering around. Actually it wasnt very noisy thats why i blew cash on other stuff like stators and exhausts, gutted. Dave 😉
|
|
|
Post by tony2stroke on Jun 9, 2020 17:29:36 GMT 1
That ring gap is almost the next size piston.
Ports raised by 2mm is not that peaky, should be OK for road use, though that would be affected if you have peaky exhausts too, should be fine with standard exhausts IMO
|
|
|
Post by bid on Jun 9, 2020 17:39:36 GMT 1
Yeah i cant believe it, he had it done at some place in nottingham apparently, What a bunch of cowboys😂🤣🤣 Thanks Tony2t😉
|
|
|
Post by bid on Jun 9, 2020 17:52:45 GMT 1
Oh also what i cant believe is the new draper compression tester was giving readings of 145psi lh and 150psi rh, which is another reason this problem eluded me for so long,
Thanks Dave 😉
|
|
|
Post by tony2stroke on Jun 9, 2020 18:17:37 GMT 1
Oh also what i cant believe is the new draper compression tester was giving readings of 145psi lh and 150psi rh, which is another reason this problem eluded me for so long, Thanks Dave 😉 That is quite high compression, maybe its just got dodgy rings, perhaps they put in your old rings by mistake, worth checking piston clearance, or dodgy compression tester maybe.
|
|
|
Post by bid on Jun 9, 2020 18:25:46 GMT 1
He gave me my old pistons and rings back they were ypvs pistons, the piston clearance on these new ones are out too like the rings, must be dodgy tester
Cheers Dave
|
|
|
Post by midlifecrisisrd on Jun 9, 2020 18:30:55 GMT 1
I think there is more to it like rings stuck in the grooves
Ring gaps are rarely as per the manual
Even the gen rings never did a lot of the time
What happens is you do the compression test is all fine
Runn the engine and when the pistons get hot enough the rings bind into the grooves
Check the ring to groove gaps before you do anything
Steve
|
|
|
Post by midlifecrisisrd on Jun 9, 2020 18:32:46 GMT 1
I wouldn't say the tester is dodgy till you check the squish
Steve
|
|
|
Post by bid on Jun 9, 2020 18:43:59 GMT 1
Cheers Steve, Ive not checked that, first job tomorrow then I wouldnt have thought of that👍 Cheers Dave😉
|
|
|
Post by bid on Jun 9, 2020 18:46:32 GMT 1
I wouldn't say the tester is dodgy till you check the squish Steve The squish is 1.2mm i checked that the other day👍
|
|
|
Post by tony2stroke on Jun 9, 2020 18:54:45 GMT 1
I think there is more to it like rings stuck in the grooves Ring gaps are rarely as per the manual Even the gen rings never did a lot of the time What happens is you do the compression test is all fine Runn the engine and when the pistons get hot enough the rings bind into the grooves Check the ring to groove gaps before you do anything Steve Very good point about the ring groove gap. Personally I have not had issues with new Yam rings being wrong on any of my Yams, but Steve has more experience with these bikes in particular than I have.
|
|
|
Post by midlifecrisisrd on Jun 9, 2020 19:04:22 GMT 1
I think there is more to it like rings stuck in the grooves Ring gaps are rarely as per the manual Even the gen rings never did a lot of the time What happens is you do the compression test is all fine Runn the engine and when the pistons get hot enough the rings bind into the grooves Check the ring to groove gaps before you do anything Steve Very good point about the ring groove gap. Personally I have not had issues with new Yam rings being wrong on any of my Yams, but Steve has more experience with these bikes in particular than I have. It's not just Yamaha's Remember not Mitaka pistons are made in Japan now Some are made in Taiwan And that's assuming it was a branded piston and not a cheap immigration or fake Another thing that will cause it is poor cleaning of the cylinder after boring As the nicely lubes piston goes up and down the bore the residue gets pushed into the ring grooves Steve
|
|
|
Post by headcoats on Jun 9, 2020 19:05:56 GMT 1
Never seen rings stained like that even on a loose bore
PJ Engineering will tell you like it is and be interesting on what they have to say
|
|
|
Post by midlifecrisisrd on Jun 9, 2020 19:09:08 GMT 1
Never seen rings stained like that even on a loose bore PJ Engineering will tell you like it is and be interesting on what they have to say Very true I've seen heads with less carbon than the sides of that piston Steve
|
|
|
Post by tony2stroke on Jun 9, 2020 19:23:19 GMT 1
Very good point about the ring groove gap. Personally I have not had issues with new Yam rings being wrong on any of my Yams, but Steve has more experience with these bikes in particular than I have. It's not just Yamaha's Remember not Mitaka pistons are made in Japan now Some are made in Taiwan And that's assuming it was a branded piston and not a cheap immigration or fake Another thing that will cause it is poor cleaning of the cylinder after boring As the nicely lubes piston goes up and down the bore the residue gets pushed into the ring grooves Steve Yes I agree with all that, It pays to learn about these bikes and do your own work, no one does it better than yourself, No snigrering at the back and taking that out of context
|
|
|
Post by bid on Jun 9, 2020 19:36:45 GMT 1
The box's he gave me were mitaka but the pistons have tkr japan stamped inside, so dont know whats happend there, i'll get the cylinders off to pjme to be checked within the next week or so, and see if all's well, as i dont have gauges to measure cylinders properly,
Cheers dave
|
|
|
Post by midlifecrisisrd on Jun 9, 2020 20:13:15 GMT 1
TKR are a good make
Think all the Jap ones are most likely made by the same company
Steve
|
|
|
Post by chrisg on Jun 9, 2020 20:26:21 GMT 1
Who did the re-bore?
|
|
|
Post by midlifecrisisrd on Jun 9, 2020 20:38:49 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
|
|
|
Post by tony2stroke on Jun 9, 2020 20:41:09 GMT 1
OH Diddly, That is worrying.
|
|
|
Post by bid on Jun 9, 2020 20:51:16 GMT 1
Hi Chrisg, I havent spoke to the builder for some time, He said he got it rebored in nottingham this was in 2018, i then had not used it much since, just to run it in, ive been fault finding since ive ran it in last summer wondering why it had not got much power, wont barely wheely in 2nd gear like my old lc's used to, Cheers Dave😉
|
|
|
Post by midlifecrisisrd on Jun 9, 2020 20:59:05 GMT 1
If that was built 2 years ago using mineral oil and not used it could well just be gummed
The only time I've had this was a looooonnnngggg time ago with an mt5
Was fitting an mtx engine in it that had been running fine then stored for a year
Would start and run fine but if you rode it as soon as you revved it it lost what little power it had
Stripped it, all seemed fine, compression tested it and all fine
Eventually stripped it for the umpteenth time, removed the rings and went round the grooves with a scraper
Ran fine after that
Steve
|
|
|
Post by bid on Jun 9, 2020 21:10:20 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
|
|
|
Post by midlifecrisisrd on Jun 9, 2020 21:12:22 GMT 1
Castor oil is bad far that
Steve
|
|
|
Post by bid on Jun 9, 2020 21:18:37 GMT 1
Shame it smelt so good,
Dave
|
|
|
Post by tony2stroke on Jun 9, 2020 21:22:24 GMT 1
Ring gap is still out of tolerance though isn't it, needs another re-bore now anyway, unless you could get away with new rings that is, maybe the rings wore fast due to contamination in the bore as Steve said earlier, swarf left in ports.
Nightmare however you look at it.
|
|
|
Post by bid on Jun 9, 2020 21:35:12 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
|
|