Vintage Dirt Bike Q & A

Great to see you back Dave, I've been reading this as a guest and awaiting your return, so I'm new here. Just seen the vid and she looks nice n responsive
I'm in UK and have owned one of these from new since 1982 (they are DT175MX in Europe)I want to ask you for some more detail on the V Force reed, is there a code number for that item? I wouldnt mind trying one of those things, do you think I could buy one into UK?

Keep up the great work

...Paul

the Moto Tassinari Vforce 3 should be available in your area.
Vforce 3 is a V382A for a 93-06 YZ 85.

the cylinder on the intake side needs to be opened up on the intake side a bunch and then epoxied between the fins around the intake area for strength.


piston is a YT175 piston and yes it fits the 1978 DT175.



for the porting i would suggest SCR racing. http://home.earthlink.net/~scloughn/index.html
BVH Racing Developments also has done a ported 1978 DT175.
here is 2 videos,the one i am building will be even stronger than this!

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(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

some engine stuff i may not had posted,this is a YT175 piston,it was chosen because it is the most like the 1976 YZ175 piston.


the sides were sanded off to prevent stress cracks from forming.


i installed the heavy duty wrist pin clips to prevent them from popping out with the high rpm this engine will be capable of.


using a Yambits complete gasket set the head was milled to a 22 cc chamber volume.


i am using a NGK B9EV spark plug in it.

_________________
(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

thats what i love about you dave..always plenty of informative photos..

i will do the best to keep it up.

_________________
(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

this is the FMF Turbine core 2 silencer i am going to use on this machine,this one for the 175 cc engine is in the 1 1/8" stinger size.


it has a built in spark arrestor and can be taken apart and cleaned. remove these Allen head screws to remove the end cap for cleaning and repacking.



for right now i have it mocked up on the bike,it has some clearance issues but not impossible ones.



what does it sound like? not too loud and pretty mellow.i have some carb jetting to do but this will commence when i get the bike ride able again.

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(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

i read on a site,RS Paint that the pinstripe on a 1971 RT1B is Sunshine Red,the same color this 1978 DT175 is.

i do need to get a tank repainted and i have a extra tank to send out and have it repainted.

here is a fuel tank from a forthcoming 1971 RT1B Enduro compared with the NOS rear fender on this DT175.




it is about dead on!!!!

before i start power tuning,i need to install this thermometer,it goes on in place of the washer on a 14 mm spark plug.

_________________
(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

Thanks for the reply re the V Force reed valve Dave, a step to far for me though all that metal removal to the point of needing to supplement the structure with epoxy< I've give up on that idea now. i do have a reed assy with the central bar removed and a single leaf of reed that I'll give a try but I might have to make some reeds from carbon fiber first because theres a small gap (bend) with one of the leaves.

I have however machined about 0.5mm off a spare cyl head tonight because they can stand it, so I'll be getting that off to the aqua blasters soonish and then give it a lick of paint.

I have a number of exhausts and silencers for mine so heres a couple of vids for you...ohh and the temp gauge, done that n got the T shirt, It's a great mod to do

http://www.youtube.com/watch?v=2i5UcEtSQTs

http://www.youtube.com/watch?v=hFEXG5oiUMc

http://www.youtube.com/watch?v=F3k49iKU ... e=youtu.be

thats a nice looking bike airhead..

nice one Airhead!

is that a factory pipe or is it a aftermarket one?

if it is Aftermarket,would they make one for me when the time comes?

would they ship to the United States?

_________________
(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

The vid with the black tank cover on the bike has a 'BigOne' exhaust, the other shows a 'Gianelli' it looks like the BigOne may still be available but the Gianelli hasnt been sold for many years, frankly I am surprised the BigOne is still sold for bikes this old. For that amount of money Dave I would give it a miss...your bike will perform just as well with the stock pipe in my experience but hey they sound nice

http://www.lm-spares.co.uk/acatalog/DT175MX_80-85_.html

make sure theres no restriction in the header pipe of the stock pipe like I found in mine

yes,that truly dumb choke sleeve,that is going to come out but there is also a additional baffle inside the pipe to be removed as well.

if i mod the stock pipe i will be sure to document it well and post plenty of pictures about it.

right now the bike has a 1990 RT180 pipe on it,these were sold as a DT180 in other countries and the pipe from one has no where near the choking the stock DT175 pipe has and is not a perfect bolt on but it does more or less fit.

here is a ride video with the RT180 pipe installed,it is slobbering rich but i have reached the limit of the stock clutch,you can hear it slip when i get it in 6th gear.

i have it running in this video with no silencer on it at all and even though it has no silencer it is no where as loud as my 1970 RT1M is which came with a pipe without a silencer of any kind on it.


click the above image to play the video.

once i get it tuned and uncorked i will have to install a set Barnett clutch plates in the hopes it will handle the power.

the clutch plates with new springs installed had the specified 2.9 to 3 mm thickness which indicates the clutch is nearly new.

it even surprised me with a couple of unintended wheelies when i played around with it in the yard in 1st and second gear.

it easily gets to 60 mph but i have went 65 mph on the bike,this machine can already give a 250 dual purpose bike a hard time once it is tuned for power with a stronger clutch installed.

i also plan to install a 26 mm YZ80 carb,right now and in this video it has a stock 24 mm carb installed on it.

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(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

latest video.i have the FMF silencer mounted and a 150 main jet installed and the needle is one clip position up from the center so i dropped the needle 1 clip.

i had the idle mixture screw set a touch lean for the temprature it was this day.

temp was in the mid 40s and yesterday it was 75 degrees which was near perfect for that 75 degree day but too lean for today.

i also installed the tto the other day and with the 150 main jet and dropped needle it never got above 420 degrees on the 75 degree day.

no top end run because it is too cold and the spokes on the rear wheel has not set yet so the loosen up so nothing really crazy here,it does rev out this time though,especially in the lower gears.

this is with the 24 mm carb and stock RT180 pipe installed with the FMF silencer installed.


it will rev to 9,000 to 9500 in the lower gears now! i need to mod the pipe internally and put on the 26 mm carb and there should be more power with more revs available then!

_________________
(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

i never went over this part so here is how i repaired the broken footpeg plus the installation of the FMF silencer and TTO temp gague.
first the repair of the foot peg.this bike came to me with the foot peg sheared off.i did have it welded but welding a mild steel part to a cast iron part has always been risky.

one day i put the bike on a jack and the foot peg soon came off.


first i drilled a 1/8" pilot hole in the cast foot peg bracket.


from there i worked up to a 27/64th bit.


i tapped it for a 1/2 13 stud i have.


i welded a appropriate size nut on the peg assembly.then i used the assembly to determine on how short to make the stud,i threaded on a 1/2 13 die to chase the threads once the stud was shortened.


once the stud was sized i assembled it,just needs paint at this stage.

_________________
(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!

then i set about mounting the silencer,it is a tight fit back there but it works.




i then installed the TTO Thermometer.
i made a small bracket that attaches to on bolt on the handle bar perch assembly.


here is the sensor at the spark plug.


this video was made after a test ride.

_________________
(2) 1968 DT1 1970 RT1M,1970 DT1C 1971 RT1B Enduro 1974 MT250 1974 DT250A (2) 1975 DT400B 1974 DT100,1978 DT175
1975 CR250M1 1979 CR250R 1979 Kawasaki KZ400H1 Jesus is Lord!!