DT175 engine rebuild - having a go and advice!
Discussion
Seen lots of build threads on here with mechanical geniuses doing fabulous work - this thread will be the antidote. A build thread by an almost-but-not-quite mechanical numpty.
Going to try to rebuild my engine following snapped ring and scored bore.
Will post pics as I go, but more importantly for me, asking for advice as I go… in case the wisdom of BB can help me from fatal mistakes.
Thanks very much in advance!
Head and barrel removed, and removing the studs (lots of plusgas first).
Going to try to rebuild my engine following snapped ring and scored bore.
Will post pics as I go, but more importantly for me, asking for advice as I go… in case the wisdom of BB can help me from fatal mistakes.
Thanks very much in advance!
Head and barrel removed, and removing the studs (lots of plusgas first).
Edited by ThreadKiller on Tuesday 21st February 17:53
Cough, big bore kit, cough, cough...
Are you just doing the engine or does the rest of the bike need attention too?
https://powersports.wiseco.com/pistons/piston-kits...
Are you just doing the engine or does the rest of the bike need attention too?
https://powersports.wiseco.com/pistons/piston-kits...
Depends what you're end goal is and budget
A fresh piston and ring, you personally clean up the cylinder and it'll be ok
Want to go next level send the barrel off to be nickel plated again
Small things when working on I've learnt
Get a forged piston
Anything that's being put back on put a dribble of 2T oil
Make sure the gudgeon pin once clipped in you turn so the open part isn't in line with the piston open bit (can't think how to explain that but you'll understand when you see it) as I've had them pop out
Use decent gaskets or OEM
That's about it really
Do they have power valves? Always clean them up as my HPP CRs get gummed up over time
A fresh piston and ring, you personally clean up the cylinder and it'll be ok
Want to go next level send the barrel off to be nickel plated again
Small things when working on I've learnt
Get a forged piston
Anything that's being put back on put a dribble of 2T oil
Make sure the gudgeon pin once clipped in you turn so the open part isn't in line with the piston open bit (can't think how to explain that but you'll understand when you see it) as I've had them pop out
Use decent gaskets or OEM
That's about it really
Do they have power valves? Always clean them up as my HPP CRs get gummed up over time
Good stuff…
I don’t think the cylinder is plated… checking this.
I was assuming I would have to split the cases and clean it… as some piston ring is missing. Probably went out the exhaust port, but can’t be sure.
So was planning on doing crank seals and main bearings at the same time.
And possibly big end bearing whilst it is apart.
I don’t think the cylinder is plated… checking this.
I was assuming I would have to split the cases and clean it… as some piston ring is missing. Probably went out the exhaust port, but can’t be sure.
So was planning on doing crank seals and main bearings at the same time.
And possibly big end bearing whilst it is apart.
ThreadKiller said:
Good stuff…
I don’t think the cylinder is plated… checking this.
I was assuming I would have to split the cases and clean it… as some piston ring is missing. Probably went out the exhaust port, but can’t be sure.
So was planning on doing crank seals and main bearings at the same time.
And possibly big end bearing whilst it is apart.
It wont be plated at that year/age.I don’t think the cylinder is plated… checking this.
I was assuming I would have to split the cases and clean it… as some piston ring is missing. Probably went out the exhaust port, but can’t be sure.
So was planning on doing crank seals and main bearings at the same time.
And possibly big end bearing whilst it is apart.
If the history is unknown, it’d be worth doing the whole bottom end, would be a real pisser to rebuild the top end for something to play up /let go and wreck a freshly built top end.
If you havent anyone in mind, I can recommend PJME in Wolverhampton regards crank rebuilds, think a rebore inc dressing the ports after and crank rebuild cost me around £130 in January.
Checking on yamaha / DT pages also say not plated so you’re right.
Already spoken to PJME and they are not too far from me, so think that’s where I will go.
I have collected NOS Yamaha little end, +1 oversize piston and rings and was intending to use those for guaranteed compatibility.
Was going to but the seals / gaskets / bearings from PJME.
I hear they know their stiff and hopefully sell good quality parts.
Already spoken to PJME and they are not too far from me, so think that’s where I will go.
I have collected NOS Yamaha little end, +1 oversize piston and rings and was intending to use those for guaranteed compatibility.
Was going to but the seals / gaskets / bearings from PJME.
I hear they know their stiff and hopefully sell good quality parts.
Edited by ThreadKiller on Wednesday 22 February 07:39
I'm in the process of rebuilding a 1989 CZ125. Remarkably, after sorting the electics it started first kick. However, a rattle became apparant and it's main bearing cages had disintegrated necessating a full rebuild. I've replaced a four stroke cylinderhead but never dealt with gearboxes or cranks before.
If you are going this far into an engine - particuarly a small two stroke - ovens are a godsend. I put my engine cases in there for half an hour at 120 degrees C and the bearings tap right out with no effort at all. Same process for removing or adding anything else. Put one thing in the freezer overnight (crank/gudgeon pin etc) and the other in the oven.
Just be aware that you will need to clean it THOROUGHLY and use a LOT of scented candles before she comes home from work!
Also, look at Viton rubber seals as they will take MUCH more heat than the standard ones and are barely more expensive.
If you are going this far into an engine - particuarly a small two stroke - ovens are a godsend. I put my engine cases in there for half an hour at 120 degrees C and the bearings tap right out with no effort at all. Same process for removing or adding anything else. Put one thing in the freezer overnight (crank/gudgeon pin etc) and the other in the oven.
Just be aware that you will need to clean it THOROUGHLY and use a LOT of scented candles before she comes home from work!
Also, look at Viton rubber seals as they will take MUCH more heat than the standard ones and are barely more expensive.
ThreadKiller said:
Checking on yamaha / DT pages also say not plated so you’re right.
Already spoken to PJME and they are not too far from me, so think that’s where I will go.
I have collected NOS Yamaha little end, +1 oversize piston and rings and was intending to use those for guaranteed compatibility.
Was going to but the seals / gaskets / bearings from PJME.
I hear they know their stiff and hopefully sell good quality parts.
I should've added about 1 oversize. On mine it would go A, B C size and you'd go one bigger depending on tolerances/wearAlready spoken to PJME and they are not too far from me, so think that’s where I will go.
I have collected NOS Yamaha little end, +1 oversize piston and rings and was intending to use those for guaranteed compatibility.
Was going to but the seals / gaskets / bearings from PJME.
I hear they know their stiff and hopefully sell good quality parts.
Edited by ThreadKiller on Wednesday 22 February 07:39
Also if steel lined easier still. I had one of my 500s nickel plated as that was orig. steel lined. Meant to improve performance/heat dispersion etc
Honestly not sure I noticed (its quick anyways) but its an option
ThreadKiller said:
Checking on yamaha / DT pages also say not plated so you’re right.
Already spoken to PJME and they are not too far from me, so think that’s where I will go.
I have collected NOS Yamaha little end, +1 oversize piston and rings and was intending to use those for guaranteed compatibility.
Was going to but the seals / gaskets / bearings from PJME.
I hear they know their stiff and hopefully sell good quality parts.
Thanks all for the recommendations for PJME, that is my company and it is me who does all the work. Already spoken to PJME and they are not too far from me, so think that’s where I will go.
I have collected NOS Yamaha little end, +1 oversize piston and rings and was intending to use those for guaranteed compatibility.
Was going to but the seals / gaskets / bearings from PJME.
I hear they know their stiff and hopefully sell good quality parts.
Edited by ThreadKiller on Wednesday 22 February 07:39
The cylinder has a sleeve fitted from the factory so can take a bore, 66mm is Std bore on the DT175
OP Let me know if you are going to pop in with it, i will try and come in and see you
Edit to say dont worry about getting the studs out, i can sort this for you, and talk you though any questions you have.
Edited by chippy348 on Wednesday 22 February 21:31
Is it nikasil? Hard to tell the surface of the cylinder is so poor! The good news is mate it was overdue a rebuild anyway with all that blowby. Get it overbored to get rid of all the damage and a bump in performance while you're at it. Also don't just slap it back together check the squish clearance, if it's miles off and it probably is, getting that right makes a huge difference.
Ah, see above its sleeved. Probably better given the situation!
Ah, see above its sleeved. Probably better given the situation!
Edited by Yazza54 on Wednesday 22 February 21:52
Birky_41 said:
Depends what you're end goal is and budget
A fresh piston and ring, you personally clean up the cylinder and it'll be ok
Want to go next level send the barrel off to be nickel plated again
Small things when working on I've learnt
Get a forged piston
Anything that's being put back on put a dribble of 2T oil
Make sure the gudgeon pin once clipped in you turn so the open part isn't in line with the piston open bit (can't think how to explain that but you'll understand when you see it) as I've had them pop out
Use decent gaskets or OEM
That's about it really
Do they have power valves? Always clean them up as my HPP CRs get gummed up over time
I'd say no to cleaning that up yourself by hand it needs boring properly. Plus going off the blow by it was overdue a rebore to get it back to round and a new piston anyway, no real loss I say OP. Needed doing. A fresh piston and ring, you personally clean up the cylinder and it'll be ok
Want to go next level send the barrel off to be nickel plated again
Small things when working on I've learnt
Get a forged piston
Anything that's being put back on put a dribble of 2T oil
Make sure the gudgeon pin once clipped in you turn so the open part isn't in line with the piston open bit (can't think how to explain that but you'll understand when you see it) as I've had them pop out
Use decent gaskets or OEM
That's about it really
Do they have power valves? Always clean them up as my HPP CRs get gummed up over time
chippy348 said:
ThreadKiller said:
Checking on yamaha / DT pages also say not plated so you’re right.
Already spoken to PJME and they are not too far from me, so think that’s where I will go.
I have collected NOS Yamaha little end, +1 oversize piston and rings and was intending to use those for guaranteed compatibility.
Was going to but the seals / gaskets / bearings from PJME.
I hear they know their stiff and hopefully sell good quality parts.
Thanks all for the recommendations for PJME, that is my company and it is me who does all the work. Already spoken to PJME and they are not too far from me, so think that’s where I will go.
I have collected NOS Yamaha little end, +1 oversize piston and rings and was intending to use those for guaranteed compatibility.
Was going to but the seals / gaskets / bearings from PJME.
I hear they know their stiff and hopefully sell good quality parts.
Edited by ThreadKiller on Wednesday 22 February 07:39
The cylinder has a sleeve fitted from the factory so can take a bore, 66mm is Std bore on the DT175
OP Let me know if you are going to pop in with it, i will try and come in and see you
Edit to say dont worry about getting the studs out, i can sort this for you, and talk you though any questions you have.
Edited by chippy348 on Wednesday 22 February 21:31
(And studs came out easily enough after some light persuasion).
As a almost-mechanical numpty, it’s the gear box that I feel most uncertain about. There are no symptoms of anything problematic, but whilst it’s apart it make sense to check it out. What I haven’t experience of is knowing what marks / wear are normal and what indicates a near in the future problem. Some more googling and videos to look into this.
ThreadKiller said:
Wow - thank you! I see lots of recommendations for PJME (not just here), and will be pleased to take you up on your offer.
(And studs came out easily enough after some light persuasion).
As a almost-mechanical numpty, it’s the gear box that I feel most uncertain about. There are no symptoms of anything problematic, but whilst it’s apart it make sense to check it out. What I haven’t experience of is knowing what marks / wear are normal and what indicates a near in the future problem. Some more googling and videos to look into this.
I can help with the bottom end, i used to offer this service but workload got to much and the shift from "engine rebuild" to "engine re-store" which i loved to do but the customer never seemed to want to pay for. (And studs came out easily enough after some light persuasion).
As a almost-mechanical numpty, it’s the gear box that I feel most uncertain about. There are no symptoms of anything problematic, but whilst it’s apart it make sense to check it out. What I haven’t experience of is knowing what marks / wear are normal and what indicates a near in the future problem. Some more googling and videos to look into this.
But for a fellow PH member i can help with your engine. If you want to have a chat just call or drop us a email, if you do call just tell them you have spoken to Paul on PH about it and i will and they will get me to the phone.
chippy348 said:
ThreadKiller said:
Wow - thank you! I see lots of recommendations for PJME (not just here), and will be pleased to take you up on your offer.
(And studs came out easily enough after some light persuasion).
As a almost-mechanical numpty, it’s the gear box that I feel most uncertain about. There are no symptoms of anything problematic, but whilst it’s apart it make sense to check it out. What I haven’t experience of is knowing what marks / wear are normal and what indicates a near in the future problem. Some more googling and videos to look into this.
I can help with the bottom end, i used to offer this service but workload got to much and the shift from "engine rebuild" to "engine re-store" which i loved to do but the customer never seemed to want to pay for. (And studs came out easily enough after some light persuasion).
As a almost-mechanical numpty, it’s the gear box that I feel most uncertain about. There are no symptoms of anything problematic, but whilst it’s apart it make sense to check it out. What I haven’t experience of is knowing what marks / wear are normal and what indicates a near in the future problem. Some more googling and videos to look into this.
But for a fellow PH member i can help with your engine. If you want to have a chat just call or drop us a email, if you do call just tell them you have spoken to Paul on PH about it and i will and they will get me to the phone.
ThreadKiller said:
Wow - thank you! I see lots of recommendations for PJME (not just here), and will be pleased to take you up on your offer.
(And studs came out easily enough after some light persuasion).
As a almost-mechanical numpty, it’s the gear box that I feel most uncertain about. There are no symptoms of anything problematic, but whilst it’s apart it make sense to check it out. What I haven’t experience of is knowing what marks / wear are normal and what indicates a near in the future problem. Some more googling and videos to look into this.
Change the selector forks if you are in any doubt whatsoever about wear on them. Usually pretty cheap on these(And studs came out easily enough after some light persuasion).
As a almost-mechanical numpty, it’s the gear box that I feel most uncertain about. There are no symptoms of anything problematic, but whilst it’s apart it make sense to check it out. What I haven’t experience of is knowing what marks / wear are normal and what indicates a near in the future problem. Some more googling and videos to look into this.
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