1978 YZ80E Rebuild

[alexbrown64]

Well, as usual i have bitten off more than i can chew.
My first real MX bike was the YZ80E.  My eyes nearly bugged out the sockets in 1978 when they arrived in the showroom. Euro white, Monoshock.. what a weapon.  Dad got me one for Christmas and i set about racing it on the sand tracks of WA.  Unfortunately, the E had a great 5 speed engine, but the frame was plagued with problems.  In fact, i broke my knee on it and 40 years later i am still feeling it.
Great looking bike and went like a rocket and lots of memories.  I have a 79 YZ80 coming so i was looking for parts.  An E pops up on Ebay with a bunch of original parts and NOS stuff.  I grab it, and now i have an E and an F coming on the truck to WA.



As this is a VMX forum, i doubt there was a kid around 78 that didnt admire the E.  The 79 F was a far superior bike, but thats another thread.

This is the old girl i have coming over...



And she also comes with these parts and more..





The guy i bought it off is a bike nut too, so we had a good chat. He has 4 YZ125K's!! That beats my two!!

Anyway, i have started to prepare for the arrival and build.  Searching for parts, the E came standard with Takasago rims.  I have found two NOS rims.  Also, i have located a NOS frame gusset kit complete with instructions.  This kit will be tig welded into the frame before blasting, zinc coating and powder coating.

Almost all the plastics are original, but i will have to use a DC front mini bike plate.  The E used the special Yamaha mounting hooks and rubber band. 
Lot of work here, but it will be a labour of love. 
Still got to get cracking on my YZ125G and all my other projects, but this is going to be fun!!

Cheers,

[80-85 husky]

cool

[alexbrown64]

Cheers Husky, yes its pretty cool to be able to buy the bikes we rode 40 years ago and do them up.

Starting to locate and collect some nice parts for the old girl.  Still NOS stuff around even after 40 years.

I dont have many pics of my E, but the one below is a 13 year old me in 1978 at the Rockingham Kwinana Motocross Club.



Cheers,

[Hoony]

i didn't have an YZ80E but would have loved one as i had the RM80B and the E engine was very torquey compared to the Peaky RM.
a cool mini being the first white YZ and monoshock.

[alexbrown64]

Hey Hoony, the RM80B was a peaky beast and a great bike.  I wanted one of those in 77, but i had a YZ80B (a slug). 
The frame on the E was flimsy and was prone to cracking and then the bike would handle badly.  I broke my knee on it, and my brother got to ride it for a few months.
Pic below of my brother Matt on my E.  There is also an RM80B (although the 6 speed C was out), and an XR75 K1.



Cheers,

[alexbrown64]

Kids were sleeping in this morning, so i could sneek out to the shed and have a play.
I wanted to check out the monoshock, so i started pulling it out.  I realized something was a bit weird around the bottom shock mount.  Turns out the swingarm has been modified to give the bike more height.
See pic of my swingarm below and the factory swingarm pic.  No problem though, as i can just chop off the extension and redrill the mount to the proper location and get it all back to stock.





If your OCD like me, then i like stuff to be pretty close to original.  I pulled the monoshock out had a look at it.  It has a bit of damping left, but not much.  Good enough for a garage queen. However, the spring will need powder coating and the body cleaning and repainting.
I removed the KYB decal, measured it up and sent a pic to Tim Lee in Canada.  He is going to reproduce it exactly in the silver and black and to the exact measurements. Pic below of my original Dr de Carbon Systems decal from my 1978 shock....



Cheers,

[mudguard]

Thats unreal Alex. My first bike was a YZ80E. Didn't race it but had lots of fun bush and quarry riding on it. Think I only replaced 1 set of rings then upgraded to a YZ80G.

[alexbrown64]

Thats unreal Alex. My first bike was a YZ80E. Didn't race it but had lots of fun bush and quarry riding on it. Think I only replaced 1 set of rings then upgraded to a YZ80G.

Hi Wayne, good story. My brother had the 80G, i had the 125G. I used to ride my E out the bush everyday, as our house backed on to it.

Got a knock on the  door this morning and the postie delivered some goodies.
My brand spanking Takasago 1.40 x 16 nos front rim arrived from the UK, together with the gusset kit (same seller)



I have a nos spoke kit that i can use to thread everything up, once i remove, blast and paint the old hub.
The gusset kit came with that funky diagram only, so it may take a bit of fiddling to get everything in the right spot.  Then i can use my newly acquired tig welder to tack it all into position, and check out the rest of the frame at the same time.

Some parts that i needed to get were a a genuine 2j5 gear shifter and rear 51t sprocket.  I found some online and promptly ordered them. Its great that you can still get these parts brand new even after 40 years.





The only problem is, i have an E and an F that i am doing up.. so sometimes i have to double up on the parts that are interchangeable.  Luckily, both bikes did come with a lot of good stuff.. but at 40 years old, there is also a lot of stuff that is too worn or just missing.

Things that interchange between the E and F are items like rims, spokes, hubs, sprockets, chain guides, front mudguards, cables, side covers, pegs, exhaust, tanks, lots of brackets and nuts/bolts.

Things i have noticed that are different are bars, levers, throttle, rear mudguard, shock, forks, frame, swingarm, airbox (i think), peg mounts, seat base and gearbox.

I have also ordered an IRC mini motocross GS-45 2.50 x 16 tire.  Believe it or not, they came out with this tyre when new.  The only difference is that the newer one is designated as 45z, while the older version was 45f.  The tyre pattern is almost identical block style.

Cheers,

[evo550]

Love your work Alex, I'll be keeping an eye on this one.

[SUZUKI311]

If anyone is chasing 16/14" chrome rims for RM/YZ80 resto's, I used Honda XR80 rims, laced up perfectly to my RM80B, $60 retail rear, $70 retail front. With the new IRC 45Z 16" front tyre, the wheel looks like its brand new.

[alexbrown64]

Thanks Evo, still gathering a war chest of parts.
Suzuki311, thats pretty interesting. That seems to be Honda part number 42701-GN1-013. At Partzilla, the retail is U.S $23. I just put the rim in the shipping calculator and it said $8 for shipping. Their computer may of bungled that calculation. Its tempting as its so cheap for a shiny new chrome 14" rim.  But its not a Takasago original :-(  What markings does yours have on the side.
Its incredible how cheap you can get new stuff for, as compared to trying to rechrome old stuff. Certainly a good option though, and thanks for the heads up.

Cheers,

[alexbrown64]

Groan......

Just received the 14" chrome rim from Partzilla.  Fantastic quality rim and would be perfect for the rebuild.. but has D.I.D. Made In Indonesia stamped on the side.  The YZ rims were Takasago and made in japan and had it stamped on the top near the nipples.  Both my YZ80's have original rims, so its off to the chrome platers at great expense..

DG had a lot of hop up parts for these bikes back in the day. Rocketfrog has an E with some great DG parts and i hope this brochure give inspiration for a build..



Ive just about got all my parts now.  Nearly everything except plastics.  Still a lot of straightening, cleaning, cutting, heating, grinding, molding, sanding, blasting, powdercoating, zinc coating, 2k painting etc.. to go but i am on track.  Should be a year or so and hopefully have an E i can sit back and look at and remember when i was 13...

Cheers,

[alexbrown64]

Crotch Rocket Factory also made a hopped up version of the YZ80E.



Cheers,

[alexbrown64]

Had another post on this, but added it here now as i have found the answers i needed.

I tried getting the old girl fired up a few days ago.  Used the cylinder and piston from the F, as i am having dramas with the E cylinder.
No spark at all.  I played with the plug, coil, kill switch etc.. but she was dead.  Time to dig deeper.  Off came the Mag cover and everything was covered in grime.  Cleaned everything up, including the flywheel, but still dead.
Time to get the multimeter out.  There are two source coils and a pulse coil on the stator.  After some help on this forum, i worked out some ball park figures for the Ohms values for the three coils, as my manual has no info.

Turns out the bad boy in the pic below has an open circuit and hence no resistance value.
Ebay had a NOS one for $15, plus reasonable shipping.  Had to fork out two bucks for GST!!
Anyway, once i get this delivered and soldered in, i can go for a spark again...

The offending item stopping me from disturbing my neighbours......


A bit of time and detective work on the old stator plate and coils....


Cheers,

[alexbrown64]

Happy new year gang.

Well, this project has been sitting in the corner a long time.  It hasn't been forgotten though, and every once in a while a gather some more parts..
Yesterday and today i gave it a bit of a nudge.  I am also rebuilding a 1979 F as well, so bits do interchange just to test stuff out.
I took both tanks off.  They were rotten inside with mud, glue and rust.. I used an old trick and filled the tanks with white vinegar and pebbles.  One tank has come up like new inside.. the other is going to take a bit longer.
I took measurements of how the decals sit on the tank. Although it is obvious where they go, i have seen some folk get them horribly misaligned.



While it wasn't nice to get rid of the original paint and decals, the tanks are both full of small dings, light rust, wear patches etc.  To keep them pristine for another 40 years is going to require a back to bare metal restore with 2k paint and clear.
The method i use it to hit everything with paint stripper, including plastics, and let them sit 10 minutes.  Does a wicked job.. then use a pressure washer.  I did both tanks and some original plastics.. all of them will take a lot of time to prep, sand paint, polish etc.  The plastics will just be sanded and polished up to a new shine.



Finally, today i broke out the big guns and did some real work.  I had the new coil for the stator, so that was soldered in and tested.  All good!  Next, i re-fitted stator, magneto, plugged in all wires and ...... hey presto.. got a spark. I added new oil to the tranny (it was empty), and had to refit some engine bolts.
I refitted the exhaust and muffler, adjusted a few bits here and there and then fitted a brand new replica Mikuni.  I am only using the replica to trial run the bikes.  The carb looks identical to the originals, and fitted perfectly.

I cleaned and checked the better of the two fuel tanks, cleaned out the petcock, added some premix and refitted the tank and connected it all up.  Ok, a little bit of "Start ya Bastard", and she fired up.
It actually idled and ran really well.  Top end is a little noisy due to issues i will post up another time, but she revved and run great.



Thats it for now.  I have to sort out the clutch rod, cover, cable etc to see if i have clutch and gears.  For now i am happy.
The F has had its cylinder re-bored, new piston, rings, cylinder head etc. Just waiting on a new wrist pin, small end bearing and piston clips.  Then i will go through the whole process with that one too.

Cheers,