DT125R owner just joined up and saying Hi

[BEng]

Hi Guys & Girls,

Just thought I would say hi and introduce myself. I have been riding bikes since I was 16, starting with a fizzer (Yamaha FSIE-DX), and over the years I have had various different types of bikes, including DT100, DT 175, X7, 350 YPVS, GS 850, ZX10, RD125, CX500, YZ 125 (road legal). And now I have a GPX 750R which I have had for about 13 years now. Although, by today’s standards it not very quick, I don’t get any problems keeping up with most people on the road. For my play thing and work transport I have a DT125R 90MY.

I have been reading this forum for about a month now whilst I have been rebuilding my DT125R, but this is the first time I have posted.

I brought my DT125R as a field bike, in not a very good state, but it ran and it was ok for the field. Then one day whilst working on the bike i noticed it had frame number, which most field bike don’t have because their nicked. Anyway I contact DVLA and got the V5 so decided to but the bike on the road, so for the last 3 months I have been buying all sorts of stuff and rebuilding the bike for the road. I have rebuilt the engine and whilst it was in a million bits I thought I would tune it up a bit, and this is where this forum has come in handy. Although over the years I have tuned lots of 2 & 4 stroke engines, it’s always handy to have some extra info about the specific engine you are working on.

Whilst I was working on the engine, I have from the bottom up, replaced the main bearings and all the seals. I have matched the transfer ports in the crank cases to match the gasket and barrel, smoothed out some of the rough edge and matched ports to flow with the barrel. Polished the crank cases around the crank shaft area, I know this doesn’t do much but I like smooth surfaces and it didn’t cost me anything but my own time.

The reed cage already had some sort of after market fibreglass reed. I don’t know of the make, but there was nothing wrong with them, so I used them. These reeds were a lot longer than they need to be so I move the reeds back to the mounting face and re drilled the 3 mounting screws, this I believe will do three things. a) Make the end of the reeds move to just 1mm passed the end of the open hole, where I wanted it. It now means I can open the hole out closer to the mounting face which will increase the intact area. c) The reed stops are now be mounted in the new position which means two things i) with out bending the stops which I believe you should never do, it will increase the amount the reeds open relative to the reed block, which will increase flow thorough the reed block, it will move the reed stop out of the way on the rear transfer port which it covers quite a lot. On the rest of the reed cage I smoothed out the opening and opened up the holes so there was open only 1mm contact around the hole for the reed petals.

I had to have the barrel rebored because it was damaged, so it is now 57.5mm. I brought a good quality piston, but still had to cleaned up the inside of the new piston the remove all the sharp edges. I added a nice 2mm chamfered the bottom edge to piston to help stop the oil from being removed whilst the piston is on the downward stroke. To finish off the piston I polished the top.

On the barrel front, I matched the transfer ports to the newly modified crank cases and gaskets (I know I said gaskets, I will come to that in a bit). I flowed the bottom edges of the transfer ports, and smoothed the whole area. I widened and slightly raised the exhaust port. This made the shape a lot better, from a square to an oval, this will help increase ring life. I then matched the power valve to the new port shape and smoothed the rest of the port, and finally polished the port. Next I measured the height I would need to arise the barrel by to match the piston at bottom dead centre to the bottom of the transfer ports. This worked out to be 1.7mm with one gasket. As a gasket was .5mm I then made a new gasket out of metal, which was 1.2mm in thickness. So now as a base gasket I have a metal plate of 1.2mm sandwiched between two normal base gasket. After I had done this I then measure the squish band clearance. To get down to the 0.9mm I wanted, I had to machine 2.1mm from the top of the barrel.

I have installed a Pipercross air filter, because the bike had no air filter at all. It already had a Dep front and rear box. I have also fitted the power valve control motor.

Although the bike is the 90MY the wiring loom is from a later bike, not sure of the year, as I brought the loom off EBay. When I have the bike "run-in", I will let you all know how it is going.

[DirtyDT]

Hi and welcome.

Some intro that! Maybe the reason you haven't posted for the month is that it took you that long to write the intro A very good intro though.

[2 Wheels]

Thats a lot of work for the wee DT.

Let us know how she gets on !

[NEV]

Hi Guys & Girls,

Just thought I would say hi and introduce myself. I have been riding bikes since I was 16, starting with a fizzer (Yamaha FSIE-DX), and over the years I have had various different types of bikes, including DT100, DT 175, X7, 350 YPVS, GS 850, ZX10, RD125, CX500, YZ 125 (road legal). And now I have a GPX 750R which I have had for about 13 years now. Although, by today’s standards it not very quick, I don’t get any problems keeping up with most people on the road. For my play thing and work transport I have a DT125R 90MY.

I have been reading this forum for about a month now whilst I have been rebuilding my DT125R, but this is the first time I have posted.

I brought my DT125R as a field bike, in not a very good state, but it ran and it was ok for the field. Then one day whilst working on the bike i noticed it had frame number, which most field bike don’t have because their nicked. Anyway I contact DVLA and got the V5 so decided to but the bike on the road, so for the last 3 months I have been buying all sorts of stuff and rebuilding the bike for the road. I have rebuilt the engine and whilst it was in a million bits I thought I would tune it up a bit, and this is where this forum has come in handy. Although over the years I have tuned lots of 2 & 4 stroke engines, it’s always handy to have some extra info about the specific engine you are working on.

Whilst I was working on the engine, I have from the bottom up, replaced the main bearings and all the seals. I have matched the transfer ports in the crank cases to match the gasket and barrel, smoothed out some of the rough edge and matched ports to flow with the barrel. Polished the crank cases around the crank shaft area, I know this doesn’t do much but I like smooth surfaces and it didn’t cost me anything but my own time.

The reed cage already had some sort of after market fibreglass reed. I don’t know of the make, but there was nothing wrong with them, so I used them. These reeds were a lot longer than they need to be so I move the reeds back to the mounting face and re drilled the 3 mounting screws, this I believe will do three things. a) Make the end of the reeds move to just 1mm passed the end of the open hole, where I wanted it. It now means I can open the hole out closer to the mounting face which will increase the intact area. c) The reed stops are now be mounted in the new position which means two things i) with out bending the stops which I believe you should never do, it will increase the amount the reeds open relative to the reed block, which will increase flow thorough the reed block, it will move the reed stop out of the way on the rear transfer port which it covers quite a lot. On the rest of the reed cage I smoothed out the opening and opened up the holes so there was open only 1mm contact around the hole for the reed petals.

I had to have the barrel rebored because it was damaged, so it is now 57.5mm. I brought a good quality piston, but still had to cleaned up the inside of the new piston the remove all the sharp edges. I added a nice 2mm chamfered the bottom edge to piston to help stop the oil from being removed whilst the piston is on the downward stroke. To finish off the piston I polished the top.

On the barrel front, I matched the transfer ports to the newly modified crank cases and gaskets (I know I said gaskets, I will come to that in a bit). I flowed the bottom edges of the transfer ports, and smoothed the whole area. I widened and slightly raised the exhaust port. This made the shape a lot better, from a square to an oval, this will help increase ring life. I then matched the power valve to the new port shape and smoothed the rest of the port, and finally polished the port. Next I measured the height I would need to arise the barrel by to match the piston at bottom dead centre to the bottom of the transfer ports. This worked out to be 1.7mm with one gasket. As a gasket was .5mm I then made a new gasket out of metal, which was 1.2mm in thickness. So now as a base gasket I have a metal plate of 1.2mm sandwiched between two normal base gasket. After I had done this I then measure the squish band clearance. To get down to the 0.9mm I wanted, I had to machine 2.1mm from the top of the barrel.

I have installed a Pipercross air filter, because the bike had no air filter at all. It already had a Dep front and rear box. I have also fitted the power valve control motor.

Although the bike is the 90MY the wiring loom is from a later bike, not sure of the year, as I brought the loom off EBay. When I have the bike "run-in", I will let you all know how it is going.

Hi BEng, and welcome to the forum, a cracking intro, if I may say so. I'm intrigued by this part mind.

"I brought my DT125R as a field bike, in not a very good state, but it ran and it was ok for the field. Then one day whilst working on the bike i noticed it had frame number, which most field bike don’t have because their nicked. Anyway I contact DVLA and got the V5 so decided to but the bike on the road,"

Did you just send off for your v5, by just putting in your vin/frame number, and no regestration number?? as I'm in the same boat, having an old 82 xt 125 with just engine and frame number. I've contacted both Swansea, who passed me on to Exeter dvla, and the pair of them have been playing table tennis with me ever since.

Would love to see some pics of your bike up on here too. if you get chance.

[Airhead]

Crikey thats gonna fly when you get her going, looking forward to seeing your progress and a few pics, why not start your own thread out of this intro's area?

Greetings and

...Paul

[barkwindjammer]

Great intro BEng, I've just finished reading it, I started reading at 5:28 GMT , yeah like Paul (Oldgit) says you should start/paste this into the 'Projects' part of the forum, its a new section for peeps like you-will be avidly reading up on your progress-best of luck with it

[DirtyDT]

Hi BEng, and welcome to the forum, a cracking intro, if I may say so. I'm intrigued by this part mind.

"I brought my DT125R as a field bike, in not a very good state, but it ran and it was ok for the field. Then one day whilst working on the bike i noticed it had frame number, which most field bike don’t have because their nicked. Anyway I contact DVLA and got the V5 so decided to but the bike on the road,"

Did you just send off for your v5, by just putting in your vin/frame number, and no regestration number?? as I'm in the same boat, having an old 82 xt 125 with just engine and frame number. I've contacted both Swansea, who passed me on to Exeter dvla, and the pair of them have been playing table tennis with me ever since.

Would love to see some pics of your bike up on here too. if you get chance.

Have a look at this thread NEV LINKY

[NEV]

Have a look at this thread NEV LINKY

Cheers,and ta for the link DDT, looks like a trip to post office and pick up a V62 form then,

Apologies for hijacking your thread BEng.

[BEng]

Yea sorry for the long intro, it started as a quick post to say hello, and I just got carried away. May I will start a new post.

[barkwindjammer]

Yea sorry for the long intro, it started as a quick post to say hello, and I just got carried away. May I will start a new post.

Wot, next May ?

kin 'Ell

[BEng]

lol, typo, that should have said "maybe"