Honda CB 125 lack of power

[pazif]

Hello any and all.

i have a Honda CB125 superdream TDC (1982).

i recently had to replace the barrels and pistons because it was leaking oil/burning oil fast then BP leakes oil in the mexican sea.

for a wile it rain o.k wile i was running in the new barrels.
after a month it started lossing power so i cleaned and ajusted the carbs.

the problem came back but the carbs wasnt the problem.

any idea what it could be, the bike struggles to 40mph and then says no.

ive checked.....

the carbs
both jets clear, all the holes in the carbs are clean and clear.

the ht leads
spark plus fire nicly, the leads ant damaged.

fuel lines
ive put a inline filter in and replaced the old hoses.

the wheels
the back wheel is alined and the chain is proply tensioned.

the wire lomb.
the wire look fine, no brakes or rusty crimps.




i thought the fuel mix could be a problem but i cant seem to get it to make a difference. the LH cylinder aperies and sounds fine.
the RH is miss firring --- (F>F>M>F>M>F>F>M>F>M).(Fire/Miss)


any advice would be great.

[Teflon-Mike]

- Where did you source the new barels & pistons?
- Where did you source the gaskets to fit them?
- Have you done the cam-chain tensioner & tappets?
- When you renewed the barel, did you use new studs?
- Did your torque the head down as per specs?
- Have you preiodically RE-CHECKED the torque on the head studs, during run in, to be sure against stretch & settle?

There's a myriad reaons why the bike could be down on power, and I ALWAYS try and work through the list, logically, dismissing the most obviouse or easily checked first.

But, something makes me think that the Head-Gasket hasn't taken.

Have you done a compression test?
____________________
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?'

[pazif]

hi.

the barrels and piston came from ebay, new but patented.

i followed the manual closely.

the studs are all the and everything was torqued as the book said.

the valves was lapped in and cheack with petrol for any leaks.

all gasgets was replaced.

the studs are arigernal. and the clearance is o.k ( LH outlet is a lil nosie)

the timing was spot on, a tooth either way on the cams sprocket was out. again i followed the book to the letter.

one thing that comes to mind....

the cam chain was very tite, a friend said it was o.k so i let it pass.

[pazif]

i forgot to say, i only put a new exhaust on 2days ago.

could this be a factor


i did a compresson test once the bike was back together, befor i started it and bioth side was 90 psi.

i havent tried a presser test since its been running.
i ant got a preshertester so i have ta wait till my friends back from hs holiday.

[Teflon-Mike]

New exhaust then sounds like a very likely culpret!
Did you use new gaskets?
Are you sure that one didn't 'drop' as you were lining the exhuast up? Often tehy end up in the header blocking half the pipe.
More comon the old gaskets sieze in the head, which they often do.
Do the compression test, that one still needs nailing.
But also the head-studs SHOULD have been re-checked after about 50 miles, and again after about 100.
Wip the rocker cover off and check them now.
Cam-chain, if its been tensioned should be reasonably tight.
Not sure about your comments about it being a tooth 'out' though?
Which exhaust did you use?
Original Twin-pipe? Pattern Twin-Pipe or Micron or Motad 2-1?
If twin pipe, have you got them aligned properly, did you hang them from the engine end, and did you get the balencer pipe locyaed properly under the engine?
____________________
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?'

[pazif]

.sorry, what ment by a tooth out is, when you set the timing the book says to line up the cam shaft with the head, to dots on the cam sprocket and TL (TLC).

all the gasgets were ariganal (they contanded asbestos) and everything was replaced, crank,head, valvesteams.

i cant check the torque or the compression ATM. (i ant got the tools for that)

i will have to wait till next week end unforchantly....

i think they might be pattern single exhausts.

i will cheack everything else in the morning....

thanks for the ideas so fare.
i will let ya no if i have any luck.

[pazif]

hi, i have fix my bike,

thank you very much teflon-mike.

i cleaned the carbs ( AGAIN ) and removed both air filters and ajusted the fuel mix.

thanks...

[Teflon-Mike]

Well Done!
But well BEFORE you go much further....... sounds like the old clogged fuel-tap, shit in the tank bug-bear!
Read this thread:- Lack of power Honda cb125tdc
Same fault, & what you need to do to stop it happening again. Basically the carbs were full of shit & the jets got clogged, becouse crud accumulates in the tannk, blocks the TINY gauze fulter on the out-let pipe, if that hasn't disintegrated, then the petrol tap on the tank, and then finds its way to the carburettor float bowl.
If you dont want to HAVE to keep taking the carbs off and cleaning them every few hundred miles when it all silts up again, you need to clean out the tank, clean out the fuel tap, and fit a little in-line fuel filter so any crud that still comes through doesn't get as far as the carbs.
Still be worth re-checking the head bolt torques and the tappet clerances though, now the bikes run-in post rebuild.
____________________
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?'