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Abarth

1970 Honda CB250k Super Sport

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After a long time of not having wheels here in London I finally found something worth getting. I was searching for an older vintage bike and as a bonus of living in the UK there are loads of old vintage Japanese stuff here, CX500's, RD350's and I've course CB's.
 
This example is a 1970 Honda CB250 K something which had been sitting under a tarp for 8 years behind the previous owners garage. Luckily the frame is rust free and the engine appears solid with 33k on the clock.
 
Its only 250cc however these motors were also built in 350cc form so a future upgrade will be on the cards which will probably be plenty for round central London.
 
I go pick it up this Saturday, plans are to tidy it up and lower it a bit.
 
Heres the pictures of when we first went to check it out -
 
yc3mydhr.ypi.jpg

 

 
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Got stuck into the bike as soon as we got it home, side walk mechanic style complete with the necessary G&T.   

 

This bike hadn't run properly for 8 years so I started off with the basics, gave it a good clean and degrease. 

 

 

eipgzkef.ori.jpg

 

 

Rust stains on everything, use the tinfoil and lemon trick on the chrome which brought it back to life. Cut the paint too which actually came up not too bad in low light

 

 

c20ziyph.a2r.jpg

 

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Removed the rear chrome parcel carrier which I'll hang onto if I ever decide to do some long distance rides.

 

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The carbs on the other hand; dang time has been unkind to these. I pulled them apart and soaked them in carb cleaner over night. After this they actually came up alright, I still need to put a proper rebuild kit in as the O rings are toast and one leaks from the float valve not shutting properly. 

 

 

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Ordered a tone of spare parts to throw at it, amazingly 95% of the parts available are genuine Honda ones. 
 
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Put in new Points, Condenser, Spark Plugs, Spark Plug Cap, Fuel Tap seals, Fuel Line, Battery, etc. Amazingly as soon as I hooked up battery everything electrical worked.
 
I put the freshly cleaned carbs back on and hooked up the fuel lines. After a fair amount of cranking she burst into life sitting there idling da.da....da.da.....da.da, 180 degree cranks have a pretty cool idle sound I reckon. 
 
Took it down for a MOT and it passed so she's all legal. Now I can focus on tidying this up and getting it running smoother with a carb rebuild.
 
As mentioned earlier rust stains, so much!! Where the chrome was absolutely gone I brought new parts to tidy it up. Still a long way to go but the previous owner threw in a full stainless hex screw kit for it too which I was stoked about. 
 
cde0ames.u3i.jpg
 
 
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On with the hotness! Makes the rest of the bike look rough as guts now haha.
 
zl4mo5qc.sfd.jpg
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Inside of the fuel tank was very rusty and kept dropping bits of rust into the fuel so I got a POR15 tank kit to fix this. First I stared with the degreaser:

 

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Then added the Metal Ready rust converted for 2 hours turning every 30mins:

 

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So far so good, have to wait for it to dry out completely before adding the final seal paint to the tank. After that it's a four day wait to let it cure before filling up.

 

Added the sealant paint, came out a bit lumpy, but coverage is good.

 

tbity5vt.tvj.jpg

 

Earlier in the week I cleaned the inside of the carbs but reused the all the old parts to get it running. Which it did but not well, wasn't making any power. I decided to give them a proper rebuild with a Keyster carb kit:

 

 

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While waiting for the tank to cure I hit the engine with a brass wire brush to tidy up the oxidation on the engine. Worked surprisingly well.

 

Before

 

yeh41pop.pj5.jpg

 

After: Other side of the engine but yeah it tidied up good.

 

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Also got the new seat cover which was for the later model one, waiting on the right one to come now but even the incorrect one tidies up the look of bike.
 
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Put some fuel in it and tried starting it after the carb rebuild and the right carb isn't running right, left one pulls RPMs no worries but there must still be an issue on the right. It also leaks like crazy with a cracked overflow pipe in the fuel bowl so I have ordered another set of carbs to build one good get out off. 
 
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Off with the seat, duct tape fix wasn't cutting it anymore so I ordered a new seat cover and set about recovering it.

 

jasx43en.tla.jpg

 

The foam underneath was actually pretty good, also drowned the metal seat pan in rust killer to tidy the underside up a bit. 

 

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Stretched the cover back on, refitted the chrome lining and strap. 
 
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The second hand Keihin carbs arrived too so I pulled them apart for a rebuild as my original ones were toast. Amazingly the insides of these replacement carbs were immaculate, I simply swapped out the rebuild kit parts from the old ones to the new and blew them out with carb cleaner.
 
Along with the new seat I put the carbs on the motor. Fired straight up and no leaks! Hooray! 
 
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Then it pissed down. Wet weather testing, after it cleared up the little Honda fired straight back up. Good to know it won't cut out riding through the rain.
 
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Riding it round after the rain felt ok, clutch was grabby and jolty like it hadn't been used in a long time. Finding neutral was a hard, I noticed a lot of slack in the tie rod between the engine and gear leaver, are they meant to have slack?
 
All and all happy with how its running.
 
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I have seen these two tools before from ye old days style.

Had never actually considered just how useful they would be for a motor bike tune. Much approve!

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I have seen these two tools before from ye old days style.

Had never actually considered just how useful they would be for a motor bike tune. Much approve!

 

 

Yeah they work mint, I set it all up initially by ear and following workshop manuals like the pilot screw should be approx 1.5 turns out etc. But I was way out, running lean with the left cylinder doing all the work. Looking forward to using this on the Fiat's DCOE's when I get back to NZ. 

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That is pretty cool. Colors instead of by ear is something that suits me. I'm pretty sure I'll these tools in my life at some point

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Cool wee bike. Drums and nice tank badges, I also thoroughly approve.

Nice work, enjoyed the colourtune pics, I've been tempted to try these myself.

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Yeah they work mint, I set it all up initially by ear and following workshop manuals like the pilot screw should be approx 1.5 turns out etc. But I was way out, running lean with the left cylinder doing all the work. Looking forward to using this on the Fiat's DCOE's when I get back to NZ. 

 

This is interesting. My CL175 never ran right even at the factory settings. Think I might give this a go. How does the carb balancer work? 

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You slap it over the mouth of the carb. It vacuum pulls up a ball? piece I assume to a number. Thats pretty much it....

I have not seen that style. Most the ones I have seen have a ball.

I don't even know why I answered this question. ....

But yeah for those players at home, its all about air bypass.

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This is interesting. My CL175 never ran right even at the factory settings. Think I might give this a go. How does the carb balancer work? 

 

 

Seedy's right it uses the vacuum from the carb to raise a little ball to a number. In this case the little ball is more of a peg shape sitting inside the orange plastic case, in the photo is hanging round the 1 on the gauge. When both carbs we in sync the gauge read about 2.5 for both carbs, do one at a time. 

 

These are the tools:

https://www.machinemart.co.uk/p/gunson-g4053-carbalancer/?da=1&TC=GS-052114053&gclid=CIfA4peDz9ACFQoB0wodavkDSA

https://www.machinemart.co.uk/p/gunson-g4074-colortune-single-plug-kit/

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There's a number of diy guides out there if you feel like making one.

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Slash just a length of hose jammed in the air intake and listen to the sound of the air rushing in.. sounds wack? Used to tune su's like that all the time.

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