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sylvaner

Dt175 Rebuild From Scratch

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When I first joined this forum I owned a 1989 DT175 3FJ.

Purchased for a massive price of $450 off Fleabay, it was sure to be a winner!

Asked the missus to take a little drive with me on a friday night.. little did she know it was a drive from frankston to horsham XD

I wanted a cheap, reliable first bike so I could find out if I enjoyed riding in the bush.. and the DT delivered.

My first ever ride through the bush was somewhere near Gembrook and I remember it pissing down with rain but having the best time of my life..

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Plenty is wrong with this speed deamon.. 

Front forks are shot, cant turn the headlight off.. tyres are wrong size.. brakes are shot.. speedo not working.. no tail light or indicators.. front headlight guard is broken.. rear suspension is way too soft.. leaking oil.. fuel mixing with engine oil.. having trouble starting.. no spark when hot.. frame scratched like it has been to hell and back.. autolube system not working too well XD 

so.. yeah.. I decided that I would try and fix some of the problems since selling this beast was no option.

 

I started with a top end rebuild to get the bike running in the first place. The bike ran.. but barely. The compression was reading in at 65psi and when I took out the piston you could clearly see a .5mm gap between the cylinder and the piston.

I had the engine re bored and put a new oversized piston in.

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Awesome mate. This is going to come up real nice, looking forward to it. Have a wiff of that kicker...a lot of leverage with that one!!

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89 means you can club permit it. Let me know if interested. I might have front DT indicators, speedo/ cable floating around the shed. If you want them lettuce know.

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Thanks for the support guys.

 

Since I wanted to fix so much on the bike, it made sense to strip the whole thing down.

I wanted to respray the frame anyway so this was the best option

Stripping the bike down revealed many problems.. including the solution to why my swingarm was constantly shifting from side to side

Not sure if you can see it but the bolt has worn down a couple of millimetres.

 

Now that the bike was completely stripped I wanted to degrees 25 years worth of neglect.. but rather then buying cans I thought I would try a bottle.

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I wanted to sort out the wiring harness for a range of issues. It seemed the previous owner(s) had spliced the headlight straight into the main 6V line. I have no idea why they did this but they sure made a mess of it. I decided to bling the harness up a tad and re wrapped it. It just made it look a bit neater.

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Getting the wiring neat was something I wanted to sort out because I thought it was the reason for some of the bikes problems.. like weak spark.

I can only see 2 points where the harness is in contact with ground. Is it worth me making a couple more ground points?

 

Thank you for the offer too Dirtpilot. I think I am okay for indicators unless you happen to have the two rear ones or the rear tail light.

Thanks again

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Hey guys,

It has been a while since my last update, however the progress is still going stong.

I have been working on the DT non stop lately and this is the progress so far.

 

I always had problems with the front forks. Every bump felt like the bike was on a pogo stick. Rather then absorbing the bumps the bike bounced over them and I found out why.

 

Here is a picture of the liquid that was inside just one fork. There was less than 100ML of fork oil in the one fork. The other fork was completely empty. It took me a while to figure out how to disassemble the forks as there is no guides that I could find on the internet.

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Forks are now rebuilt and have stopped leaking oil =D onto the next part

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I wanted to tackle the problem where I had fuel mixing with the engine oil. Turned out I needed to replace the crank seal (93102-25061 and 93103-28011) as they were leaking bad.

 

You can see just how rich the bike was running before I took it apart. This is the carbon build up after just 200KM

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Bored out the exhaust a little too.

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During the disassembly I was trying to screw a screw into a piece of the framework so I could paint it. well I was holding the frame when the screw snapped off and the remaining half went straight into my knuckle.. had to wait for 6 hours in the hospital before it could be removed XD

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Here is the swing arm before primer.. completely stripped of any surface rust.

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After 2 coats of primer

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and final 3 coats of silver.

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When I first purchased the bike it looked like somebody was running old engine oil through the autolube system instead of 2 stroke oil. needless to say I think the autolube system needs a full clean out

The gasket was stuffed but I couldn't be bothered ordering from Yamaha for the 300th time so I decided to make one

 

inside the system I found lots of sand and lots of old oil build up.. hopefully she will run a little smoother.post-2586-0-54914300-1399805216_thumb.jppost-2586-0-70708000-1399805287_thumb.jppost-2586-0-39062100-1399805371_thumb.jppost-2586-0-42274700-1399805463_thumb.jp

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Going well with the old girl!! I've had two of that model & two 82 models, great bikes. The earlier models had a thinner head gasket & gave the newer ones a bit more poke when it's used, also running a long 8mm drill bit through the silencer & opening up the air box makes a great improvement. Be careful of the head bolts, it's easy to pull the threads out.

I think I wanna buy another one now! Lol

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This project was finished a while back, I thought there was no interest on this forum so I didnt bother.

 

I ended up shaving .5 off the head to give her more squish. 

I also took off the muffler as it was extremely restrictive and replaced with an open ended 2t muffler.

This really opened the whole bike up through the rev range. She pulls much more aggressively and makes it heaps more enjoyable to ride.

Its no WR450 but you can still enjoy thrashing it around the bush and going absolute **** full on down the straights.. just dont trust those drum brakes.

 

The problem with the bike which prompted me to rebuild it was it seemed to not get spark when it was hot.

Turned out to be the seal in the engine had come loose and was feeding engine oil through the piston which was completely fouling the best of spark plugs.

I went through the whole wiring harness and breathed new life into this bike... which seemed like a complete waste of time the first time dad and I went to the sand dunes XD enjoy the pics guys =D

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sure will, better be dry though! wouldn't trust that rear tyre in the conditions we're used to haha

I've got a couple of rears in the shed, 1/3 worn but free to a good project.

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hmmmmmm I might have to hold you to that!  :pallanatale-01: Would be pretty surprised if you have anything close to a 4.10x18x4pr.. they're old school measurements though.. I had a 110 but I had to cut the side knobbies and they still rubbed after major surgery 

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hmmmmmm I might have to hold you to that!  :pallanatale-01: Would be pretty surprised if you have anything close to a 4.10x18x4pr.. they're old school measurements though.. I had a 110 but I had to cut the side knobbies and they still rubbed after major surgery

Dam, I think I threw out the 90/100 off the KDX.

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I just thought I would share how the old DT is looking today. Just replaced the Stator and autolube assembly.

 

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Its looking a tad worse then a few months ago, but the missus and I have had some fun riding it around the bush.

 

Here is the video of when my autolube and stator failed

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Usually they are a small pump that has lines running to the crucial parts in the bottom end, so you don't have to premix fuel. Some people still do just for reassurance.

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Hi Sylvaner,

Love the build. I'v started getting my an old DT175 91 model back running and ready for registration.

I need to do the oil in my forks as you did. Do you know what oil you put in the forks? 

Do you have any tips to completing the work - getting old fork apart etc?

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Hi Styleswon, I have recently done a rebuild on a DT 175, mine's a 93 model but early 90's models are pretty much all the same.

Doing the forks requires some tools that most people wouldn't have in a standard toolbox. From memory you will need a 19mm allen key to get the top cap off.

Also I think I needed to machine down an 18 or 19mm socket to get the rebound dampener out from down inside the fork tube. This stuff needs to come apart if you have to replace the seals.

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By the way, nice thread mine for your first post

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Nice thread - great old bikes IMO.

Can't be too many people that HAVEN'T ridden one at some point  :)

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