CB125 - 2 into 1 installed - Not running right.

[supra3turbo]

Hi There,

Since all my problems with my CB125 stemmed from bad carburettor rubbers, i got a 2 into 1 manifold, only to find the bike is exactly the same.

The bike starts and idles nicely, but as soon as it hits around 6-7k its miss-firing, cracking and popping. If you touch the throttle any more it just bogs totally.

I have tried the needle clip right at the top (lean), and at the 3rd notch, nothing seems to make a difference.

Its like it just dumps fuel in and cant fire it, or at these revs, the spark goes intermittent or something.

It may also help to let people know that I have the Jailing JH125 copy engine in there, which I believe has a 360 degree crank, so i had to wire the single black red wire into the white and blue wires on the CB harness.

I have had this bike and engine running great, although at the moment I am really struggling to come up with any more ideas.

Does anyone have any suggestions?

Thanks all - Joe
____________________
Hoda CBR 600 FX stolen from stalybridge 2017/2018 black
Current Project Suzuki RG125 Cafe Racer

[supra3turbo]

Haha, I always seem to post boring threads asking too many questions

Anyway, I have found that the problem is the 2 into 1 with no filter is sucking the fuel and air in much to quickly for this shitty chinese engine, it just bogs when revved.

If i put my hand over the carb inlet a bit and cause some resistance the bike revs fine.

It must be resistance has the needle at fully rich causes it to barely run, and at fully lean it revs to about 3k now then bogs right down.

What can I do to help this, I have at the moment put a 6 inch long rubber tube on it with a sponge inside, this has helped quite a bit, although the carb poped and blew the sponge out, is there anything I can make or do just to get this running right?

I just want my RG off the road to make pristine again, and use this as a winter run about.

Thanks all - Joe
____________________
Hoda CBR 600 FX stolen from stalybridge 2017/2018 black
Current Project Suzuki RG125 Cafe Racer

[at106]

If putting your hand over the inlet helps i would say the bike is currently too lean. Is your air filter oiled and fitted correctly and have you checked for air leaks?

[supra3turbo]

I dont have an air filter on the bike at the moment, not even sure if ive got the manifold on the right way, i wouldnt be able to put a cone filter on it as it would hit the frame, which is making me think that the manifold is upside down.

I have tried the bike at its richest position (clip at the bottom) and its even worse, its like its all too much for the bike too soon, I'll have to make a video of it to explain it better.
____________________
Hoda CBR 600 FX stolen from stalybridge 2017/2018 black
Current Project Suzuki RG125 Cafe Racer

[at106]

Reading your OP again the carb rubbers were bad so you replaced the manifold, did you also replace the carb rubbers?

Really you need to have an air filter otherwise you'll just cause more problems, if you dont want to you could try covering half of the intake with tape and see if that helps. But it sounds to me like an air filter would provide the required restriction.

[Teflon-Mike]

you wont be able to get a filter on the carb on a single manifold, it will foul the mono-shock upper mount.

But no great worry; they ought to run pretty well 'open'. It wont screw the mixture THAT much on that engine. Just mean you'll get a bit more shit sucked in and your carb needle may wear out a bit faster and you might have to adjuste the tappets more frequently to allow for the higher rate of valve seat regression

What you got, with 360 lump and single carb is pretty much stock Benly set-up. It wont rev out like the Super-Dream anyway, due to soft cam; it'll top about 10K ish.

Mid-Range flat-out though?

1/ check the gaskets in the carb & manifold. The rubber O-Rings are NOT exactly unknown for going hard and not sealing. Use paper to be sure.

2/ That exhaust. I'm guessing it ent a new Motad? Probably be worth more than the bike if it is! So Second hand, and probably twenty years old.

Check the headers for pin-holes. Get brutal with the rotary wire They tend to go on the bends where metal stretched thinest; esp bottom bend where condensation collects and they rust from the inside.

Pin-holed header is garanteed to make motor run weak and rough and give symptoms you describe.

But while you are about it; crush washer gaskets; they are about 50p, get new ones. Leaks at the manifold are not good and these are rather notoriouse. Gaskets often get nipped up 'cock' in the rebates.

Bottom of headers, also prone to being dinged 'curbing' the thing. Dings dont tend to choke the flow enough to make bike run bad; but does take the chrome off, and leave score where they will rust through. From port to collector, make sure the pipe is whole, or these motors will never run well.

After that? Well... Have you checked the tappet clerances? And HAVE you checked the correctly? OTMH the tappet clerance is something rediculousely daftly thin, like 0.005" and they oft get set to 0.05" as people mis-read the noughts or presume a typo, or just dont have a feeler guage that narrow!

If them basics dont help?

Then my suspicion would be that the rings / bores shot. These motor's like tight rings, and when worn, they float and stop sealing at revs and under load.
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[supra3turbo]

Ahh Teff, not heard from you for a while how are you

I Basically got the stock duel exhausts, and cut 6" off the back of each for sound, does sound well but im guessing ive messed it up.

The bike with the true honda engine and twin carbs ran a treat with my custom exhausts, i could run it slightly richer and it ran well, right to the redline.

Since the rubbers went to bits, I just took it off the road waiting until i could do something with it again.

So if I put my 2 into 1 Micron exhaust back on, with some back pressure again, will it work better with this single carb.

The reason I decided to cut my exhaust is it sounded quiet as hell with the micron on it, and a kid stepped out on me, first quiet stock exhaust ive ever had and after that I thought sod it, loud is safer, i live in an area where children seem to be brought up by simpletons lol.

I will check the O rings round the manifold, and I will also upload a video too.
____________________
Hoda CBR 600 FX stolen from stalybridge 2017/2018 black
Current Project Suzuki RG125 Cafe Racer

[supra3turbo]

I went to a super sprint do a while ago watching bikes (some CB250's) that just sounded amazing and deafening so I tried to copy that, hence me cutting my exhaust, and I was damn close to it at full chat haha.

Here is a video of it first starting with the single carb, but the reason I am only reving it that much is any more and it bogs down, the blue smoke I put down to a stuck ring, this does not smoke anymore.

https://youtu.be/upIj_4Mcb4k

https://www.youtube.com/watch?v=upIj_4Mcb4k&feature=youtu.be
____________________
Hoda CBR 600 FX stolen from stalybridge 2017/2018 black
Current Project Suzuki RG125 Cafe Racer

[motad_uk]

[quote="Teflon-Mike"]you wont be able to get a filter on the carb on a single manifold, it will foul the mono-shock upper mount.

But no great worry; they ought to run pretty well 'open'. It wont screw the mixture THAT much on that engine. Just mean you'll get a bit more shit sucked in and your carb needle may wear out a bit faster and you might have to adjuste the tappets more frequently to allow for the higher rate of valve seat regression

What you got, with 360 lump and single carb is pretty much stock Benly set-up. It wont rev out like the Super-Dream anyway, due to soft cam; it'll top about 10K ish.

Mid-Range flat-out though?

Good advice!- interested in your view about the value of the exhaust!

we are going to make some of the "old"/discontinued Motad systems over the winter in stainless- is there anyone out there interested in us making some CB125 TD ones?

MOTAD UK

[supra3turbo]

Would it be possible to make a cafe racer style exhaust maybe? Something gold star looking/Siamese style headers type thing, the cafe racer look is really taking off again as everyone knows and these bikes with their classic shape really look the part with clip-ons.

I have put my Micron exhaust on the bike again, and its exactly the same, so i stuffed my carb inlet with sponge and it runs upto 6k just.

Not sure what I can do to it now, ive checked everything just loosing patience with it again, the old engine ran perfectly with split rubbers, i used it every day, just took it off the road to bore and cam chain, think ill just do that engine and stick it back in.
____________________
Hoda CBR 600 FX stolen from stalybridge 2017/2018 black
Current Project Suzuki RG125 Cafe Racer

[motad_uk]

[Teflon-Mike]

[Teflon-Mike]

[motad_uk]

[quote="Teflon-Mike"]

[supra3turbo]