Vintage Dirt Bike Q & A

i repainted these parts with this.


the kick stand and bash panel.

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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!!

now to get the frame ready for repaint.
my power washer.




this tag is all but destroyed but i had one reproduced for it,it will come later.


the turn signal mounts were bent so i straightened them.


removed the triple tree.

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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!!

now to remove the fork lock.






now to give the frame a coat of paint.

_________________
(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 repop data sticker.


now i can reassemble the frame.
first the fork lock,to reinstall just thread in the knurled portion.


then lightly tap it home.


reinstalled the bash plate.


reinstalled the swing arm.

_________________
(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 the completed short block back in.




my stage 2 ported top end and piston arrived.


i also got a Moto Tassinari Vforce 3 reed valve assembly.


this piston is for a YT175 and was chosen because it is the most like the 1976 YZ175 piston but the ring stop being pinned the way they are is compatible with the 1978 DT175 cylinder.

it was lightly massaged for the application.

_________________
(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 head was machined for a 22 cc chamber volume to bump up the compression a bit for the stage 2 porting.


the wrist pin keepers are a heavy duty type should this engine see 10,000 rpm.


now to button her up.


ignition timing was set to 1.8 mm BTDC.


there is 3 marks to align,1 on the flywheel,another on the cases and 1 on the stator.

_________________
(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!!

oil pump is set up.


i installed a RT180 pipe,these are not nearly as restrictive as the stock 1978-81 DT175 pipes are.


there is a choke sleeve installed on the stock DT175 pipes which was designed to reduce short circuiting which is the exhaust port and transfer ports are open at the same time.this was a EPA mandated thing.here is a stock pipe for a DT175 pipe on the exhaust port side.
this is the RT180 pipe inlet.


this is a stock DT175 pipe inlet.


the pipes are very close but the RT180 pipe has a slightly shorter stinger.


this is a RT180 pipe side by side with the DT175 pipe.



the mount tab is a little different but it can be worked with.

_________________
(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 repaired a stripped hole but i have not picture of the stripped hole so i am using a pic of the air cleaner mounted up,i am indicating the stripped hole with my finger.


i used this thread setter,without it the only ways to repair it is with a Heli coil or drill out and weld a replacement nut on the other side of the bracket.




i got a good used rear inner fender to replace the one that was badly damaged on the bike.


after i cleaned it up some.


the CDI box bracket was missing a rivet plus the other one was loose,i drilled out the old one and used plastic rivets to fasten it to the rear inner fender.




other side of the rivet.

_________________
(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!!

good luck with all the dirt in your engine after the rebuild.

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80 CR250Ra
80 CR250Ra
78 CR250R
80 CR80
82 Bultaco Sherpa 340
78 Bultaco Pursang 250 MK12
76 Bultaco Frontera 370 MK10
76 Bultaco Alpina 250
73 Bultaco Lobito 125 MK6
76 Suzuki RM125A
90 Kawasaki KX250

the engine i assure you was clean when it went together.remember we are talking about a heavily abused 35 year old bike,the bike was produced 3-77 and was registered in 1977 even though it is a 1978 model,there was no 1977 DT175 here in the united states but there was a twin shock one released in Europe in 1977,the mono shock was a 1978 and later feature.

i have videos on this running and others with the electrical tests as well that will get posted later.

i have other bikes and i rebuilt the engines in most of them.

don't go off half cocked!

i did a lot of cleaning on it as it was truly nasty,here is the cases,one clean and one dirty,perhaps you should study them closely.


here is a video of it running and i was going to post this later.click the image to play the video.

_________________
(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 fork seals need to be replaced,here is the rebuild of them.
the new seals.




to remove these covers i used a screw driver and tapped with a small hammer.




i flushed out the dirt with a solvent then removed the wiper and replaced the seal.


cleaned and inspected and replaced the wiper.


then i put the cap back on.

_________________
(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!!

here is a picture of the freshly assembled fork.




i did the same with the other fork as well.these gaiters were not put on all the way and they are a aftermarket part and they don't fit quite right.


the is the upper clamp of the triple tree freshly repainted.


freshly repainted and rebuilt triple tree.


the fork gaiters don't fit very good so i will have to find a better set,i have located some NOS gaiters but they are very pricey for what they are.this will come later.


they may fit the smaller forks on a GT80 or DT100,the 78 and later DT125 takes the same part the 175 takes.

_________________
(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 picked up a set of instruments and bracket,other than the faded plastic in places were in good shape.




one of them removed and you can see the fading,i ended up dusting it with paint and it restored the color somewhat.




i went over the bracket some with this stuff.


after a bit of work with the fine polish.

_________________
(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 took apart the ignition switch to paint the housing.




i reassembled the switch,at least it looks a bit better than it did.




the finished gauges and bracket.

_________________
(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!!

these are some before shots on the handlebars.i am reusing what i can due to potential part unavailability and cost.




i worked them over with some chrome polish,they look decent and it is a improvement.




i mounted them on the bike.

_________________
(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!!