Yamaha 1975 RS125 Rebuild

[michael_meineck]

I have a lovely vintage stroker with a little problem, it doesnt work.

I have decided to first get it running, then MOT'd so that i am satisfied it is worth my time and effort to do more, then, I will try and restore a little of its former lustre the intention being to strip it down, re-paint the frame and all the green bits, and re-chrome the forks...

Ill document this little enterprise here for anyone interested, and as a total novice, if you spot me doing something glaringly stupid... do tell me

Mike

[stinkwheel]

You'll probably find you can get new, pattern fork stanchions for less than the price of re-chroming the old ones.

I'd imagine a lot of YB and RXS parts would fit too.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[michael_meineck]

so all i knew was that it didnt run and needed a battery

poking about has revealed the following

fork seals gone, what fork seals?... for that matter what fork oil?
all the cables are shot
on removing the tank i tried to remove the fuel lines and they split, which led me to discover they were full of a rather glue like substance which i suspect is also the cause of the sticky carb

there are a lot of screws either rusted in place with the heads rounded, or just with the heads rounded + an additional screw i ruined trying to remove it

the electrics look like corrosion and rust so i might have to make myself a new wiring loom however ill test when the battery (and other parts i have purchased through ebay) arrives


the engine does turn over which is a plus as seized would have been upsetting
the chain, sprockets and tyres are in beautiful condition


since I wrote the above and forgot to post, I'll add that i have removed the front wheel and inspected the brakes, all perfect working order there, additionally i pulled out the forkstook them apart as far as i could, cleaned them up and drained the smidgen of oil (which was a greyish blackish sludge) and am now stuck

this suspension setup has the spring on the outside of the stanchion, my problem stems from there being no circlip holding the seals in place, and no bolts in the bottom holding it all together, so how does one dismantle the thing? see attached

I might have to get a manual

[stinkwheel]

Definately get a manual. You'll be needing it.

Some of the forks on small bikes just pull apart, you sort of bang the stanchion up like a slide hammer. I don't know if that is the case with yours though.

That stanchion looks really tidy on the picture, oughtn't to need re-chroming.

Just take the carb off, strip it and clean it out. From your description of the fuel line, I 100% garauntee is isbunged up solid with varnish-like brown crap.

Get yourself a big can of penetrating oil and an impact driver. Those cross heads are a total nightmare. Also get a drill and a pair of mole grips so you can drill the heads off those ones that are totally knackered and undo the stumps.

Replace the cross heads with good quality socket heads or torx heads. Also get a tub of copper grease to coat the threads of any bolts you replace with it so they come out next time.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[michael_meineck]

an impact driver, I am surprised one has never made it to my tool kit before I'll definitely get one asap as ill be making no progress without it, bought a manual on ebay dedicated to the RS models as having owned and RXS i know they are different in many subtle ways

Thing is with the stanchions, (ill post a picture later) they arent desperate but they have 32 years of gradual degradation, there are pitts on pitts and rust painted over at the bottoms, I am not looking to get it concours, but i would like to get it looking as good a three year old not hacked machine so sorting out forks, replacing mudguards and repainting would get me 90% there, the engine will never be much improved on, one of the cooling fins is broken

and i will certainly be checking with Mr Haynes before i go hulk hogan on the stanchions

do you have any projects on the go?

[stinkwheel]

Aye. https://www.bikechatforums.com/viewtopic.php?t=152245 should be getting ANOTHER spare engine for it tomorrow.

I've been maintaining/doing up my girlfriends YB100 for the last 12 months. You have my sympathy about the cross head screws!

Another top tip for those is to fit an impact driver bit in the chuck of an old fashioned drill brace. Jet someone to brace the far side of the bike and you can press almost all of your bodyweight on the screw head as you attempt to turn it.

I have actually twisted impact driver bits doing this (honda CB125T oil pump screws)!

www.vehiclewiringproducts.co.uk sell anything you could possibly need for the wiring, including the proper, non-insulated bullet terminals. They also sell all the cable, outer, ferrules and nipples to solder up your own control cables.

www.wemoto.com have a surprisingly large range of consumable spares.

If you need to get at the points, a Honda C90 rotor puller fits the YB100 and cost less than a tenner.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[ms51ves3]

[michael_meineck]

ms51ves3

very shiney, I am going to break out the autosol and I will attempt that before shelling out on new forks or chroming

Stinkwheel (interesting name?!) thanks for the tips thats an interesting project you are undertaking, I have never ventured too far into an engine, where did you come by your obvious experience?

do you think you can find a working one?

I have had a challenging morning with the bike... there are no shops in the whole of guildford selling impact drivers so i thought id take another look at the forks and voila discovered how to take them apart

I also destroyed 1 x pair needle nose pliers, 1 x screw driver, several dremel cutting tool bits and a chisel getting out 1 x fork seal - pictures to follow, now i know what i am about I suspect it will only cost me another chisel to get the other one out

[michael_meineck]

Update on todays progress

Got both forks apart and the seals out... checked the bushes for wear and all is fine, the stanchions have some pitting but not enough to worry about i dont think.

awaiting delivery still on new seals so will use the time this weekend to clean up fork legs

managed to buy an impact driver in nearby Godalming (cost me £18.75 ) but was only place i could find it, it worked a treat so removed the airfilter box and pipes, it turns out that the air filter is a JAY cloth with masking tape
again will clean up these bits this weekend and repaint since they are off

took the carb off as was sticking but it doesnt seem to be in bad condition at all (if you discount the slightly bent long pin thing, the trouble is that when i attempted to refit with the new throttle cable etc i discovered it (the gold tube thing) really doesnt want to go back in properly, its sticking even worse and i tried lubing it with carb cleaner and even WD FORE tea, do you have any ideas or suggestions? perhaps the carb is fairly universal and i can just get a replacement

Ill take some pictures tomorrow if its not raining of the foliage and insects i have pulled out of every orrifice of the bike

[Endless Nameless]

Blimey, thought our H100 was a project! Good luck with this, nice to see people working on fixing up old stuff- it'll be a bloody nice bike when you're done!

Only thing I will say is work out how long you think it'll take, and how much you think you'll spend.

Then triple both. That'll probably be more accurate

It'll be worth it though
____________________
A2 passed 22/07/08; restriction up 22/07/10 (just so I don't forget)
'79 Suzuki GS550E. Yes, that's a GS550, not a GS500.
Supersports "In a video editing competition I'd kick your sorry ass"

[michael_meineck]

[Endless Nameless]

H100, search 3 men and a dog in this section. Not been updated in a while, had a full engine rebuild recently and just being put back together for the umpteenth time! Funny enough, that was to stop us spending our student loans on getting ratarsed. We started out on trying to properly restore it, but ended up going for a similar aim as you- very sensible to decide that from the start, although cosmetically yours looks a lot better than ours. The H is now mechanically well sorted, and all the MOT bits are spot on, forks etc, it just looks shabby. Next year it's gonna get tidied up a bit too.

Then we'll have to buy summit else and do it again... I fancy a 4t 250 this time round! Project bikes are just waaaay too much fun.
____________________
A2 passed 22/07/08; restriction up 22/07/10 (just so I don't forget)
'79 Suzuki GS550E. Yes, that's a GS550, not a GS500.
Supersports "In a video editing competition I'd kick your sorry ass"

[michael_meineck]

and cleaning up the airbox pics to follow

how do you guys keep patience? my seals and battery havent arrived so i cant test the engine or put the front back together this weekend... SOOO annoying

and Endless, I am already finding i agree with you on the cost part... I have totted up money spent and its already unpleasant reading.. though I spent too much on the seals, i bought them direct from Yamaha :-S

i have decided to put it all in a spreadsheet from start to finish so we can all go Ouch!! when done

[ms51ves3]

That air filter is classy

[michael_meineck]

re-built the forks.. the new seals came in and I had to push them back in with bits of polyeurathane piping and a big vice, I have a little problem, I dont know how much and what weight oil to put in them?

Yamaha Dealer helpfully only has records back to the 80's so if no one has a clue i willl take a wild stab and see how it rides

also, put in new battery and guess what... a great bit nothing... I checked the fuse and connections but still not a spark of life so i am buying a new multimieter and checking out the wiring.. it looks shite so it probably is suffering corrosion

I am feeling dejected... it should have been running today