Makita Piston
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Hi! Just got my barrel and Bits’s back from pjme’s and have a question about Makita pistons. where does the ‘crinkly’ backing ring thing go? Top or bottom ring? I know that the top is a keystone ring and the bottom is plain, but i don’t know which one has the backing ring thing...
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Makita? Cool I never knew they moved into Piston manufacturing now
Is this taking the "Power" band to the next level.
You mean Mitaka don't you?
I think that's the bottom ring, but I have NEVER bothered fitting it and I've never seen it on any other DTR Piston. RS didn't have one either.
Make sure you measure the Piston Ring End gap and ensure it's within tolerance!
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Yeah. Mitaka. I called it something entirely different in the thread title and edited it to Makita. How embarrassing?!!
The barrel and piston have just come back from PJME so I trust the tolerance, ect. The barrel is a 3MB and it says TZR on the piston box. I’ve never had one like this before but I have seen them online in pics, ect.
The piston that was in before was a wossner. Both the rings looked identical, so I don’t really know what to make of it all. Just want to get it right, what with being the sixteenth ‘registered’ owner. I feel I have a duty of care for the old plodder
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I wouldn't assume anything. Checking the ring gap will take you 60 seconds per ring.
It's literally just placing the rings at the top of the bore. Use the piston to push it a few centimetres in and making sure it's square. Then using a feeler guage to measure the gap where the rings butt. It should reside within tolerance.
I find the Wossner ones always supply one ring out of spec. Presumably so you can fine tune it yourself.
Do that for both rings make sure they are tip top. Then whack them in and away you go.
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Hey Calum, where can these tolerences be found? I suppose its in the service manual? I dont own a manual but maybe its time i pull the trigger on one
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@Arild 0.30 - 0.45mm you'll want a decent small file. And only file inwards towards the centre of the ring. I hold the file in a vice and slide the ring along the jaws of the vice to help keep it all square as well.
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@SpookDog ive installed one and left one out can’t remember which bikes but the dt probably has one and I’m sure I tried one with and without on an am6 engine and it appeared to make no difference I don’t actually know what it’s for most people don’t install them.
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Thanks mate
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Soooo, it’s an expander ring, for bores that have a bit too much clearance. Goes behind the thinner ring, on the bottom of the piston. Not recommended to be fitted if you have a nice tight fresh bore...
Got an email from PJME -
@SpookDog moar compression!! Will do 109 in 4th gear with that in then
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@declan
Wow, I wish I lived in the same reality as you...
I think
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I mean, typically that's how it goes. The higher the compression the more power. Typically.... You need fueling and ignition timing to accommodate.
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When my dt was running 225psi it had incredible midrange but wouldn't rev high.
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225PSI! Wow! That's mental.
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@Calum that was a cold engine aswell! That's with +1mm over bore. Running a mick abbey modded head. Which is quite a few cc's less volume than stock 3mb.
Runing two base gaskets and a spacer plate now. To lower the compression which has also raised the port timing. I miss the heaps of midrange but not the bruised foot from kickstarting it lol. -
Yeah I bet
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@declan
Sorry, didn’t mean to offend. Plus I gave
up a looooong time ago! 
In all seriousness, I’d like to know what the cc of a 3MB head is? Mine had to be reprofiled to get rid of piston ring explosion marks and I’m not sure if it was skimmed to the point that it kept the same compression ratio
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@SpookDog I measured one of my heads at 13cc, unfortunately can't remember which. The dome of the +1mm mitaka piston measures at 3.5cc though : p
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Cheers bud, that’s something to work with. I’ve got a good 3bn, my reworked 3mb and another 3mb (that I forgot about till now) that is battle~scarred but otherwise original.
