Hybrid Project - RD250 AC/F2

[toffee]

I had a long running thread on the old forum for my hybrid project which stalled in early 2017
because of a few things like motivation, Interest, finances and time but I started thinking
about the project again a few weeks ago. Its currently taking up a lot of space in the garage
and under the bed so I want to close it out and also try and get it dry built so that I can
register it here in Ireland. The frame is still registered in the U.K and I figure the process
could get a little more complicated post BREXIT.

There will be a lot of images but small 100kb ish file sizes.

So I will start the thread here but condense it as much as possible and try a post a timeline
as to the project progress from when it started in:

February 2013

with a 1975 RD250 B engine which lets face it looked horrendous. I bought it cheap with carbs
but missing a cover or 2.

After a false start with a different frame I bought a "roller" from Northern Ireland, an RD350F2
which came with a YAMAHA YSF-R125 swingarm which is a popular mod to the frame around:

September 2014

[toffee]

February 2015

First task was to ditch the standard swingarm and fit the YZF unit with a previously bought
Honda Varadero XL125 rear wheel [which was to fit in a different swingarm and of the right
profile to take a 120 wide tyre]

Fitting the swingarm also meant fitting the YZF shock and fabricating new linkages.

A knock on issue was the swingarm fouling the L/H rear set so both had to be angled for clearance.

[toffee]

February 2015

I split the cases so early in the build because I wanted to get the crank rebuilt and rather then
lifting the engine in and out to get it mounted in the frame was going got be a pain in the back

December 2016

I was able to get the crank delivered and rebuilt in the U.K cheaper than buying the parts
and having someone do it in Ireland.

March 2015

The engine mounting session was a mammoth one, of course the air cooled engine had slightly
different mounting points and I spent a lot of time shifting and lining up the front and rear sprockets
while making sure everything was centered and straight with clearance of the frame and swingarm.

[toffee]

March 2015

Engine mounts finalised, brackets fabricated and welded in place.
The top rear mount will actually be changed as in the right hand plate will sit on the inner
side of the frame mount with a shorter spacer used.

[toffee]

March 2015

After fitting the swingarm and earlier fitting a front end with an Aprilia RS125 unit I got
the bike leaning properly on fresh rubber with aid of a Honda CBR600 sidestand.

Next up I test fitted a set of Codnor Micron exhausts from an RD250LC which fouled the
sidestand so mods had to be made to the sidestand.

[toffee]

Its 2020 and we are in social distancing mode and possibly entering a country wide lockdown
because of COVID-19 here in Ireland and oh yes its St.Patricks Day! Happy Paddys Day to all!

There is all of a sudden lots more time to work on other stuff like finishing my project . . .

So I will continue the story from where I left off about a year ago.

March 2015
After sorting out the side stand I moved onto fitting the pipes properly and sorting the issues
which popped up.

Because of the wider swingarm the pipes and end cans wouldnt clear the arm,
I took the plunge and cut the end can off the left hand exhaust. This enabled me to mount
the main body of the exhaust to the engine/frame to check the side stand clearance and spring
location.

The end can will have to be extended by a minimum of 125mm to clear the swingarm. The image below
shows it extended fully by about 200mm. This also places it wider than before.

Also at the header end of the pipes there was a clearance issue,
I cut a length of pipe to simulate the header length and offered it up to see how the exhaust on the left
sat. There are two issues,

[1.] the inside rib on the Micron exhaust clashes with the cross bar of the frame but this can be ground
down to clear in that particular spot and welded to re-seal if needed, this will also have to be done with
the right side too.

[2.] the end can as mentioned before clashes with the swinger which is wider on the left for the chain run.
I am planning to slice a piece off the inside at a straight angle and weld a flat piece back on. This will
only affect the padding inside and not the baffle itself. it shouldn't be too much to remove, approximately
20mm in and about 50mm in length . . .

June 2015
I made a start about stripping the frame totally while the front end was off. I flipped the frame and installed the
engine cases with the barrels and heads in order to finalise a solution for the left side exhaust pipe. I think I have
sourced a suitable bit of mild steel pipe to extend the silencer past the swingarm.

After sourcing a suitable length of pipe with the correct bore I cut a section with angled ends
to extend the end can of the left pipe to clear the swingarm. The end can will be extended by about
70mm. The original internal stinger has been cut to be welded in place where it would normally be
with the other end with the silencer being able to fit back into the end can. The stabilizer strap will
have to be remade to span across the 3 sections of pipe.

The images below show the pipes taped up to give an impression of the layout/run of the pipe.

And the finished product...

[toffee]

In between getting the kick stand and exhausts sorted I got proper lockstops fitted,
the top yoke and bars fitted, refurbished the front forks along with refurbishing an
original set of clocks which I purchased off one of the members here! I also got
an old Stanley headlight modified with some plastic welding [I think the headlight
bucket is actually fibreglass?] Oh yes and I also refurbed a set of original switch gear which
was got from this forum!

[toffee]

Between March and June when the pipes were finished I also managed to get the rear calipers sorted.

I had to have the rear carrier modified to mount the Honda Varadero caliper and carrier to the swingarm with a piece welded in to mock
the Yamaha YZF carrier, this is how it sits now. this has to be painted and fully finished.

[toffee]

July 2015

Front caliper fully refurbished with new pistons and seals

I also got the gear shift linkage sorted using and modifying some spare aprilia RS125 parts
which I had in my RS125 bank!

[toffee]

July 2015

The project started to take a bit more shape after fitting the wiring loom and working out the
routing and what exact loom I had, again sourced from the old 2strokeforum.

[toffee]

Fast forward about 16 months to November 2016 and I collected the heads, Barrels and side casings
from a company I sourced which specialised in Vapour Blasting. Absolute stellar job to say the least.

I couldnt have dont this myself, couldnt have gotten in between the cooling fins to clear away all the old paint
and oxidisation.

My plan is to paint the crank cases black, polish the side casings and leave the barrels and heads bare

[toffee]

December 2016

Sent the crank over to the UK to be built, I couldnt find anyone in Ireland
who could do it and I got it rebuilt in the UK cheaper than I could buy
the parts myself.

I got it done with http://firefoxracing.co.uk/

[toffee]

January 2017

I managed to source 2 identical branded pistons as a kit, with rings, Clips and Gudgeon Pins.

I couldnt find any info regarding the "Made in Taiwan" Speed brand and labeled for RD250DX

The tolerances work out pretty good and are as follows:
Cylinder oversize measurement: 0.035 - 0.040 = 0.035
Piston Ring end gap: 0.25 - 0.40 = 0.30
These are approximate measurements with feeler gauges.

...and this is the last I worked on the project until earlier this year

[toffee]

2020

I invested in an ultrasonic cleaner and proper solution to clean the grubby carbs.
I had previously purchased new parts from Yambits to complete the rebuild, New jets, needles, choke, seals and screws.

So after a good going over with a dremil and stainless steel brush I removed the old paint and oxidisation and then
gave them a good cleaning in the UC.

Next up I need to make a list of what parts I need to complete the job and what tasks I need to do on the bike to finish

[85RZwade]

Wonderful details and a great story; I can relate to much of it myself! You've taken some bold steps and I'm anxious to see more of your progress.