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cb125 probs

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Garth84x
Two Stroke Sniffer



Joined: 13 Sep 2009
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PostPosted: 19:36 - 13 Sep 2009    Post subject: cb125 probs Reply with quote

hi all, just got meself a '84 honda 125 twin (superdream) for use after my cbt, it may be old but is in quite good condition.

however there is a problem with the running side, bike starts fine, if a bit noisy, cam chain i expext, the idle is random revs/drops, as soon as the throttle is touched it bogs down and dies.

any ideas what this could be? as im new to bikes.

thank you

garry
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Fisty
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Joined: 11 Apr 2007
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PostPosted: 20:07 - 13 Sep 2009    Post subject: Reply with quote

Mine did this till I balanced the carbs then all was fine.

2 new air filters and a carb balance should do it.
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Garth84x
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Joined: 13 Sep 2009
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PostPosted: 20:17 - 13 Sep 2009    Post subject: Reply with quote

thank you ill give that a try. although it may be worth metioning that the air filters are the k&n type, i didnt fir them they were already on it.

also is there any way of adjusting the cam chain.

garry
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 15:38 - 14 Sep 2009    Post subject: Reply with quote

They don't like pod filters. Does it still have the original airbox?
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I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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Garth84x
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Joined: 13 Sep 2009
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PostPosted: 17:47 - 14 Sep 2009    Post subject: Reply with quote

yeah, the guy gave me it with the bike, i tried it but it seemed to run worse?

howerver i have a new problem Sad i took the rocker cover off to see the condition of the cam chain etc, and went to make a cuppa, i came back just in time to witness my 3 year old dropping a washer into the engine. cant see it, think it has gone all the way down Crying or Very sad Crying or Very sad

needless to say it must be retrieved, any suggestions please Embarassed

Garry
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 20:41 - 14 Sep 2009    Post subject: Reply with quote

Garth84x wrote:
yeah, the guy gave me it with the bike, i tried it but it seemed to run worse?

howerver i have a new problem Sad i took the rocker cover off to see the condition of the cam chain etc, and went to make a cuppa, i came back just in time to witness my 3 year old dropping a washer into the engine. cant see it, think it has gone all the way down Crying or Very sad Crying or Very sad

needless to say it must be retrieved, any suggestions please Embarassed

Garry


Turn it upside down and shake it. Magnet on a stick. Turn the engine slowly by hand and see if it comes back up stuck to the oil on the crank flywheel.

Invent a time machine, go back to when you took the rocker cover off and stuff a rag down the camchain tunnel before you touch anything else. Wink

Re. the initial problem, could also be an air leak at the inlet manifold. Also check the throttle needles are still attached to the throttle valves, they are held in by a pretty flimsy spring clip, mine used to come adrift if you didn't put them baqck in absolutely square.

Also check the cam timing is not one tooth out (loose camchain could jump a tooth, it would probably run but not at all well).

To tension the camchain, loosen the nut on the back of the engine located between the two carbs. Press down on top of the camchain tensioner (you should feel it move) then tighten the nut while still pressing down. It's supposed to do it automatically by means of a spring when you loosen the nut but the spring is a bit weedy.
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“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.
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Garth84x
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Joined: 13 Sep 2009
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PostPosted: 21:34 - 14 Sep 2009    Post subject: Reply with quote

Thank you, fpr the relpy, ill give it a go tomorrow, if the washer dosn't fall out, guess ill have to stip the engine then Crying or Very sad

Garry
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 22:02 - 14 Sep 2009    Post subject: Reply with quote

I've heard of people greasing the flywheel in the hope that it'll pick the offending article up from the bottom of the crank when turned by hand. More often on 2-strokes to get dropped small end needle rollers. Works sometimes.

You can also sometimes get them by pushing a magnet on a stick in through the hole where the oilpump pickup goes (if it'll fit, can't remember the exact setup on a CB125). Bits tend to gravitate to the lowest point which is where the pickup usually is.
____________________
“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.
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Garth84x
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Joined: 13 Sep 2009
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PostPosted: 22:20 - 14 Sep 2009    Post subject: Reply with quote

thanks again, ill guees ill just have to see what i can do.

one more thing bike is a 82 cb125 twin, im looking for a cam chain but i am unsure what one i need, had a look on wemoto, but the pics of the chains dont look any thing like mine.

anywhere else i could try?

thanks again.
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 22:28 - 14 Sep 2009    Post subject: Reply with quote

Hi

Is it a superdream (electric start) or the older CB125T (kick start)?

All the best

Keith
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Garth84x
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PostPosted: 09:39 - 15 Sep 2009    Post subject: Reply with quote

its a superdream, 125 twin,elec start, there are listings on wemoto for TDC/TDE/TDJ, etc i dont know which one ive got, new to bikes.

sorry for askin silly questions.

Garry
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 09:46 - 15 Sep 2009    Post subject: Reply with quote

Hi

At that age it will be a TDC. It is very early for a Superdream though.

All the best

Keith
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Garth84x
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PostPosted: 15:22 - 15 Sep 2009    Post subject: Reply with quote

Thanks for that keith Very Happy

progress is being made, thought i'd have a look at the carbs while im waiting for some bits to arrive, the piston in the right hand carb is sitting a lot higher than the left at rest, methinks this is while it was behaving badly.

Garry
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deliriousthun...
Spanner Monkey



Joined: 29 Mar 2008
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PostPosted: 15:40 - 15 Sep 2009    Post subject: Reply with quote

Might be naïve, but I think worth suggesting, as we all miss the obvious from time to time.. Maybe you've accidentally left the choke on?

EDIT: oops, didn't read your last post properly, sorry Razz
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Garth84x
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PostPosted: 14:30 - 16 Sep 2009    Post subject: Reply with quote

Ive made a start, took the engine apart, and im guessing from the look of things that the bottom half of the engine has to be split to change the cam chain. (and to retrive the washer, and whatever else i find)

straight forward i thought, however i cant remove the um..flywheel? magnet thingy lol, sorry any one know if has a left or right handed thread and how i can lock the engine to remove the nut

thank you.

Garry
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 14:48 - 16 Sep 2009    Post subject: Reply with quote

Garth84x wrote:
Ive made a start, took the engine apart, and im guessing from the look of things that the bottom half of the engine has to be split to change the cam chain. (and to retrive the washer, and whatever else i find)

straight forward i thought, however i cant remove the um..flywheel? magnet thingy lol, sorry any one know if has a left or right handed thread and how i can lock the engine to remove the nut

thank you.

Garry


For removing the nut, if you've not dismantled the clutch/gearbox yet, putting it in gear and holding the rear brake on is often enough to stop things turning. You can also put a strap wrench round the outside of the flywheel. Air impact wrenches are fantastic for this so if you're stuck, take the whole engine down to your local garage and they'll be able to whizz if off in about 5 seconds.

You need a flywheel pulling tool to actually remove the flywheel from the crank. It's something utterly obscure like a 27mm x 1.0 reverse thread (don't quote me on that).

It's a case of either buying or borrowing one, a genuine honda one costs a tenner. Takes seconds to pop one off with the proper tool, takes hours without and usually lands up damaging something. Careful not to lose the Woofroffe key when you get the flywheel off. The Honda flywheel pullers fit quite a lot of bikes, even other makes.

Honda part number: 079330010000
https://images.cmsnl.com/img/products/flywheel-puller_medium079330010000-01_b3bb.jpg
____________________
“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.
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