'73 CB250 - Doing it right this time round.

Re: '73 CB250

Hi, get the fairing back on!!! Not often you find one with as good lines as the one you have. I think you should go with your original colour scheme on the jacket, it would look similair to the one in that perfume advert? You know the chanel' one with Keira Knightly, think it's a Guzzi though..
By the way I think I am just over the bridge from you. :)
 
Re: '73 CB250

Check it out!
Picture1119.jpg

This could be you..... 8)
 
Re: '73 CB250

wab said:
You know the chanel' one with Keira Knightly, think it's a Guzzi though..

It's a Ducati SS Bevel !
But the manufacturing land was right ;)

And I dig wab's opinion !
Your fairing is badass, keep it on and do a vintage racer style it definitly will look superb !
But it's just my opinion, as long as you enjoy building and riding everything will be fine ;)

-Sven
 
Re: '73 CB250

Looks pretty sweet with the fairing on there, man. I'd keep it for sure :)

That's the direction I want to go with my CB175, full vintage racer setup. Did you weld up your own mounts for the fairing or manage to bolt it on somehow?
 
Re: '73 CB250

wab said:
Hi, get the fairing back on!!! Not often you find one with as good lines as the one you have. I think you should go with your original colour scheme on the jacket, it would look similair to the one in that perfume advert? You know the chanel' one with Keira Knightly, think it's a Guzzi though..
By the way I think I am just over the bridge from you. :)

Yeah, I saw that and started looking at a beige/cream theme, then found the jacket. I'm gonna spray it grey to start seeing as I already have the paint, and if it doesn't look right i'm definitely going to go for the scheme on the jacket 8). Ah yes you are just over the bridge, not too many active UK members on here let alone local haha.

ponieswhee said:
Did you weld up your own mounts for the fairing or manage to bolt it on somehow?

The mounts are bolted. on. The rear mounts connect to the base of the battery box and front is clamped and bolted to the downtube.
 
Re: '73 CB250

Not much to report at the minute. For some reason its just lost spark so no starting her up for the minute. Between a slight cross-threaded head and a clusterfuck of dodgy wires and connections, this is gonna take some time :mad: haha.
 
Re: '73 CB250

a-ha! (As Mr. Alan Partridge would say). The lack of spark issue may have been solved. Could of diagnosed the problem quicker if I could find my multi-meter, but it seems to be the left side coil. So another one is on its way.

Apart from that, I replaced most of the bolts I could undo (Most are extremely rounded and an absolute b*****d to undo) with stainless allen head bolts, and Ive primed the carb tops.

Also wheeled the bike out into the sunshine to get a better picture as it currently sits :).
 

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Re: '73 CB250

Ok, Im not great with bikes so i'm gonna need a bit of help here.

Sorted out the wiring and coils so now she starts and idles. The idle is pretty inconsistent as it seems to occasionally rev itself and then slow down. Once the throttle is twisted, the bike dies. But this is only for the left carb (when I use move the throttle arm on the right carb it revs fine, but on the left, it dies)...Is this just a sync or timing issue...maybe throwing too much fuel in from the left side?
 
Re: '73 CB250

I'd check the condition of the plugs to see whether you're rich or lean on that side then adjust the carbs accordingly. And verify the float levels are ok as well.
 
Re: '73 CB250

ponieswhee said:
I'd check the condition of the plugs to see whether you're rich or lean on that side then adjust the carbs accordingly. And verify the float levels are ok as well.

Put new plugs in a few days ago and the left side is much darker and sootier than the right. So I adjusted the mixture and it now runs a little better, but it still seems pretty temperamental. Once its revved and the throttle closed off, it still revs for a second after and doesn't fully shut off....Its difficult to explain so Ill try and get a video up as soon as.

So while I waited to do that I decided to start on the seat today. Managed to strip the old paint and put the first few coats of primer on.
 

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Re: '73 CB250

More....don't know how to put more than 4 pics in a post.
 

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Re: '73 CB250

Still having a few problems with the bike running. Left side header is much hotter after a 5 minute run than the right.

Took apart the carbs to change float level. Whilst they were off the bike I gave a few parts a lick of paint. The throttle arm is Hammerite smooth black with new a stainless bolt and the tops are Plastikote gold. (Even though its plastic paint, it seems to be holding up well)...sorry for the poor quality, they were taken on my laptop.
 

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Re: '73 CB250

Did a bit more work on the seat. It only had a few scratches and knocks in it so luckily I didn't need to do a lot of filling. I used Loctite body filler as it was the cheapest on the shelf (£6 for 280ml of filler paste + 15ml of hardener) and it seemed to hold up well and was easy to use (I suppose filling was never going to be too hard in the first place anyway! haha)
 

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Re: '73 CB250

Started sanding it back with 180 grit wet and dry. Then moved on to 240 then to 320. Seemed to leave a nice enough finish to give it another few layers of primer, but I decided to leave it til tomorrow as it was getting a tad dark. Need to be setting up a paint booth with some decent lighting next I think haha!
 

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Re: '73 CB250

When I first got my 175 I had to play with just about everything to get it running right. Firstly the floats were off so bad the gas would just pour out of the overflows, fixed that then dropped the needles a notch which helped lean it out a bit. Also the throttle cables had been routed badly so the revs would rise when the bars were turned. The little CBs are very sensitive to throttle cable routing, might want to make sure the cables are moving freely. What helped the most was nailing down the ignition timing, which was way off...
 
Re: '73 CB250

ponieswhee said:
When I first got my 175 I had to play with just about everything to get it running right. Firstly the floats were off so bad the gas would just pour out of the overflows, fixed that then dropped the needles a notch which helped lean it out a bit. Also the throttle cables had been routed badly so the revs would rise when the bars were turned. The little CBs are very sensitive to throttle cable routing, might want to make sure the cables are moving freely. What helped the most was nailing down the ignition timing, which was way off...

I don't think the timing is too bad at the moment (famous last words) but I'll have a lil tweak later and see if it helps. The biggest problem I'm having is definitely with the carbs. The fuel literally just pours out the over flow no matter what height I set the float to so I'm beginning to think the float needles aren't the correct ones (the rest of the bike was a bodge job so it wouldn't suprise me). I can't seem to find anywhere on line where I can buy them either. The carbs are the Keihin 725b model.

The other issue I'm having is occasionally when I take the carbs off to clean or reset float height, once assembled again, the bike starts and just revs itself almost full throttle (Cable routing is ok I think). And then one of the headers runs MUCH hotter than the other. Could this be down to the mixture or any other carb issue?

Bloody carburetor's are beginning to get on my nerves to be honest! haha
 
Re: '73 CB250

Setting the float level is a pretty important part of the carb tuning. If you're still getting overflow that means your gas level in the carbs is too high so you'll be running rich, which is consistent with the black, sooty plug. It could be that the floats are getting hung up on something or that they have holes in them and don't float any more. Generally the leaner the mixture the hotter it burns, so if one header is way hotter than the other it's probably leaned out or might be leaking air into the mixture from somewhere.
 
Re: '73 CB250

Ok, was going to check the timing but I couldn't find my multimeter or a timing light. But the left point seems to just open on LF (on the stator) and has a pretty consistent 0.3-0.4mm gap throughout the process, the same with the right. So until I can set it properly and double check its right I just cleaned the contacts up with a bit of emery cloth and re-installed them.

I was wondering why there was a constant flow of fuel from the overflow pipe no matter what height the floats were set to. So I took the carbs apart again to give them a clean and check and found a small hair-size crack running down the brass fuel overflow pipe. So I'm guessing that was the problem. Anybody know of a way to fix it? I was just going to solder it up but I'm not too sure if that would work.

I also found a small crack on the rubber intake boots that connects the carburetor to the head. So as a temporary fix until I can get another one delivered I covered the crack with silicon bathroom sealant. (It's white in the pictures but when fully dry it's transparent).
 

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