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DT 175 MX Engine Rebuild


philmountains
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DTEngineRebuild001.jpg

Hi All well having a break from the electrics saga, and sort of starting on the engines/s the one on the left is a 125MX the right one is the original 175 I started off with, and there is another one in bits under the bench,I have three 175 barrels all need something, be it bent fins on one ,this one has a piston at .50re boree this has been buggered with, one exhaust stud drilled out to 8mmm, but have made a 8 to 6mm stud,bores look ok, then I have another ,the original one with a chunk out of the bottom of the barrell unfortunatly just at the point were the cylinder head bolt fastens down, think .50re bore"only used vernier calipers so not 100%" but apart from that very clean and straight,then the last old and abused at ? think it was .70re rebore and scored and exhaust studs both 8mm but this could have the donor bit off alloy to re weld onto the original head.

Waiting for a gasket set and cannot find my impact screwdriver so will be a bit of a sporadic start :huh: also yesterday strippeded down and rebuilt ignition switch as had a original yam key and ignition but had wires cut so matched up to a good base and wires ,also made up a 6volt battery charger out of a old push bike light charger ,that,s saved a few quid.

will post a few pics of barrels son for your amusement/ appraisal. :lol:

Read a artical in a old motorcycle mechanis on 175MX, never start with a basket case,oh Bo------cks

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...........and cannot find my impact screwdriver so will be a bit of a sporadic start :huh: ..............

Hey Phil try your locker at work ;)

..............,also made up a 6volt battery charger out of a old push bike light charger ,that,s saved a few quid.

........

Buy three more batterys and charge all four with this :P

DTEngineRebuild001.jpg

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Hey Phil try your locker at work ;)

Buy three more batterys and charge all four with this :P

DTEngineRebuild001.jpg

Never ever do a bike build like this unless certified insane :blink: here are the pics !!!!!

This is the worse

DTBarrels008.jpg

and it errrrr piston

DTBarrels007.jpg

The left bought from ebay years ago, comp with piston,bloody shame about fins ,you bet they snap if try to bend back! the right the original nice clean, straight fins just a big chunk missing from base :angry:

DTBarrels005.jpg

can you see the bit missing ?

DTBarrels004.jpg

can you see the slag hole on the exhaust port "quality control" :lol: also the droppy crow bar to the head fins

This is were it all get,s stupid again :o want to use this crappy crankcase, cos the silly numbers stamped on it, match a frame I have(£25 in the post at mo to DVLA) but am not using at mo as the frame building is a hell of allot nicer, but will at some time in the fairy tale future with the help of the lottery win :lol: captain bodgit has been at it with his welding gun and let the big end run free ,or old broken rings have done some extra alloy removal work to it.

DTBarrels001.jpg

here is the welding

DTBarrels002.jpg

well paul did a bit off a job to a bloke at works laptop, and he,s only gone and given me a impact driver, so wont be looking in the locker ,there deff aint no more ,pressies comming out of them :lol:

Just thought I would pop this pic on as I thought that the 125MX and 175 MX shared same bottom ends or is it a year thing again ? look at clutch basket and gear wheel at base of basket.

DTClutchBasket001.jpg

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.........Just thought I would pop this pic on as I thought that the 125MX and 175 MX shared same bottom ends or is it a year thing again ? look at clutch basket and gear wheel at base of basket.

125's have one less friction plate, and generally look different

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How far do you want to take the word 'same'. There are tiny differences right through the bottom end. To be exactly right the only 'identical' components will be the cases themselves.

The gear ratio's electrics etc are all just a tiny bit different, BUT, you can swap a 125 top for a 175 top with no issues. You can swap clusters, you can swap primary drive sets.

Side by side there will be many slight differences. But as far as it matters they are the same.

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How far do you want to take the word 'same'. There are tiny differences right through the bottom end. To be exactly right the only 'identical' components will be the cases themselves.

The gear ratio's electrics etc are all just a tiny bit different, BUT, you can swap a 125 top for a 175 top with no issues. You can swap clusters, you can swap primary drive sets.

Side by side there will be many slight differences. But as far as it matters they are the same.

Hi guys ,not doing this strip for science,just thought I could try and use best bits to make 1 good one,anyway brought a puller home from work to get flywheel off and not a bloody chance,so have caved in and ordered "Proper Job" tool,shame as cash spent on this could have gone towards bearings.

Am I showing my true yorkshire self here ?

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brave project phill" Skipton " theres a few Yorkshire strokers meeting there sat, for a ride-out, Get you KH out , giv her a blast,, B)

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brave project phill" Skipton " theres a few Yorkshire strokers meeting there sat, for a ride-out, Get you KH out , giv her a blast,, B)

Hi Blackhat Dont know about "brave" Barmy might be muted by others ,still love these little bike though.

are they going? up to Kirby Lonsdale? ,unfotunatly KH has not run since 1992 :lol:

Thanks anyway do hope to have DT going soon though, so may be next time ,only prob I have only get 1 weekend of work a month.

Thanks Phil

How your DT comming on is it finished yet,you mentioned May, would love to see a pic

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Hi Blackhat Dont know about "brave" Barmy might be muted by others ,still love these little bike though.

are they going? up to Kirby Lonsdale? ,unfotunatly KH has not run since 1992 :lol:

Thanks anyway do hope to have DT going soon though, so may be next time ,only prob I have only get 1 weekend of work a month.

Thanks Phil

How your DT comming on is it finished yet,you mentioned May, would love to see a pic

Will post a pic later isnt there always a bloody screw thats a bitch ! could be last one ,spoted it earlier though so !!!someone not a Jap, had snapped a impact driver head into head of phillips screw the one in the corner behind generator flywheel, sorry about this to you well endowed people is this the corect term :lol: but the chisel had to come out as absence of dremal ,no probs and no damage.

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"sorry about this to you well endowed people is this the corect term "

Erm no, but you wouldn't want it on the end of your nose as a wart.

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Ok Boys Engine in bits,Bearings, seen crankshaft on Ebay,Poss overpriced ? what about the rest anyone changed the lot any info appreciated ,also getting them out ? Nev what about Lumiweld rods ?

Thanks again

Phil

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Ok Boys Engine in bits,Bearings, seen crankshaft on Ebay,Poss overpriced ? what about the rest anyone changed the lot any info appreciated ,also getting them out ? Nev what about Lumiweld rods ?

Thanks again

Phil

DON't buy cranks of ebay if you already have one. If it ain't broke etc. Check the main bearings against spec and if all good put it right back, rough rule is sideways play of upto a mm or so is fine but no, as in zero vertical movement. If it is out of spec its cheaper in the long run to have it rebuilt, someone like PJME will rebuild a little crank like the DT for 25quid pluss parts.

Main bearings and seals can be done using the bearings in the freezer engine in the oven method (watch out for the wife) the rest of it to quote Mr Haynes is a reverse of the removal process pretty much. Follow the manual and don't rush.

What are you refering to when you say "getting them out", if the motor is in bits?

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Don'tt buy cranks of ebay if you already have one. If it ain't broke etc. Check the main bearings against spec and if all good put it right back, rough rule is sideways play of upto a mm or so is fine but no, as in zero vertical movement. If it is out of spec its cheaper in the long run to have it rebuilt, someone like PJME will rebuild a little crank like the DT for 25quid pluss parts.

Main bearings and seals can be done using the bearings in the freezer engine in the oven method (watch out for the wife) the rest of it to quote Mr Haynes is a reverse of the removal process pretty much. Follow the manual and don't rush.

What are you refering to when you say "getting them out", if the motor is in bits?

Hi Cynic ment getting bearings out of casting as you mentioned oven we are on the same wavelength,going to to take bits to work tonight give a good clean in parts washer, and will have a good look for wear etc..got new gasket set + seals ready need some gasket glue for casings though.and rush well got too many projects on the go to rush + cash issues !

I must say that buying that flywhel puller was worth the money, had it off in 10 mins yesterday morning.

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Ok Boys Engine in bits,Bearings, seen crankshaft on Ebay,Poss overpriced ? what about the rest anyone changed the lot any info appreciated ,also getting them out ? Nev what about Lumiweld rods ?

Thanks again

Phil

Well Phil I can honestly say I've never used them, and reading about them see that its not really welding as such, and not even brazing but soldering, good though I see for crap alloys like monkey metal, and dear mind £15 quid for 5, probably using 2 or 3. Tell ya what I'd do mate, I'd find a local stainless steel speciallist firm (bound to have a TIG plant knocking about), some back street one somewhere pretty close to you, take your case with you around about dinner time 12.30 -1.00 ish, find the chargehand or foreman, explain your predicament, he'll find one of the lads on their dinner break that will be able to TIG it up for you 10-15 mins,and I reckon you could precure his services for a "drink" about a tenner, i.m.o. jd mate, or we're back to liquid metal route, or theres another type very similar to Lumiweld and thats Techno-Weld, not sure how these compare in price mind.

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Hi Cynic ment getting bearings out of casting as you mentioned oven we are on the same wavelength,going to to take bits to work tonight give a good clean in parts washer, and will have a good look for wear etc..got new gasket set + seals ready need some gasket glue for casings though.and rush well got too many projects on the go to rush + cash issues !

I must say that buying that flywhel puller was worth the money, had it off in 10 mins yesterday morning.

Whenever I've had to get bearings out of castings I've used a little GENTLE heat around the casting, and loctite do a freeze spray to spray on the bearings, at the same time, so a combination of both should get the pesky little beggars out, oh and a tip I use for putting new bearings in, is to bang them in the freezer in clingfilm, or a sandwich bag, for a few hours, makes life much easier for putting them back in. Just my ten penneths worth.

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Hi Cynic ment getting bearings out of casting as you mentioned oven we are on the same wavelength,going to to take bits to work tonight give a good clean in parts washer, and will have a good look for wear etc..got new gasket set + seals ready need some gasket glue for casings though.and rush well got too many projects on the go to rush + cash issues !

I must say that buying that flywhel puller was worth the money, had it off in 10 mins yesterday morning.

The easiest way is with a heat gun, turn the case so the bearing will drop onto the bench then heat the back of the casing with the heat gun. Ally expands faster than steel and clunk out they drop easy as you like. No physical force on the cases at all.

You can use one to put them in too, again heat the cases with the gun to what they call 'iron hot' ( where spit sizzles) and then take the bearings and drop them in. You don't want the bearings ice cold just ambient. Its the crank you want ice cold as that will then slide easily into said bearings. The seals also go in far easier with the cases hot, then once the whole lot is in position let it cool and all the parts will 'grow' together. Very effective method as not using any force means the bearings are really snug and true. Certainly not going to move.

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The easiest way is with a heat gun, turn the case so the bearing will drop onto the bench then heat the back of the casing with the heat gun. Ally expands faster than steel and clunk out they drop easy as you like. No physical force on the cases at all.

You can use one to put them in too, again heat the cases with the gun to what they call 'iron hot' ( where spit sizzles) and then take the bearings and drop them in. You don't want the bearings ice cold just ambient. Its the crank you want ice cold as that will then slide easily into said bearings. The seals also go in far easier with the cases hot, then once the whole lot is in position let it cool and all the parts will 'grow' together. Very effective method as not using any force means the bearings are really snug and true. Certainly not going to move.

Thanks lads for advise/tips will def take note, the crapy case with the engine number I want to keep ,the bearing feels rough so was going to swap these ,do you reckon and to save cash could use bearing fom other case ?

Yeh Nev them Lumiweld rods are dear, and reckon only good for gluing, no penetration so poss not up to what I need them for .

any thoughts on trying to staighten up the fins ?

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=270738962861&ssPageName=STRK:MEWAX:IT

Thanks again

Phil

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Thanks lads for advise/tips will def take note, the crapy case with the engine number I want to keep ,the bearing feels rough so was going to swap these ,do you reckon and to save cash could use bearing fom other case ?

Yeh Nev them Lumiweld rods are dear, and reckon only good for gluing, no penetration so poss not up to what I need them for .

any thoughts on trying to staighten up the fins ?

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=270738962861&ssPageName=STRK:MEWAX:IT

Thanks again

Phil

There a tenner a go you tight bastard. :P

ALL the bearings and seals can be got from TY Trials for under 100 quid. I repeat thats every seal and bearing all genuine. For under 100 quid

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There a tenner a go you tight bastard. :P

ALL the bearings and seals can be got from TY Trials for under 100 quid. I repeat thats every seal and bearing all genuine. For under 100 quid

Cynic you know what they say about Yorkshire men :D ,will check out TY Trials,by the way saved a fiver+ by doing a search for the bearing puller and then got cash back from quidco site, and yes I buy all my cloths from charity shops :lol:

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Cynic you know what they say about Yorkshire men :D ,will check out TY Trials,by the way saved a fiver+ by doing a search for the bearing puller and then got cash back from quidco site, and yes I buy all my cloths from charity shops :lol:

Something to do with ferrets and warm beer?

Seriously, it will cost massively more to replace all the gaskets if that bearing only lasts 6 months.

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