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Advice needed - Bike will idle but not rev! - update sorted

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Mr Calendar



Joined: 14 Jun 2004
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PostPosted: 19:58 - 09 Oct 2010    Post subject: Advice needed - Bike will idle but not rev! - update sorted Reply with quote
Had a little bit of drama with one of the bikes.
Old, 1985 CG125, in need of TLC eventually got running and through MOT. It's a little project bike, like to get it restored a little more rather than rat it.

However, on a little test ride the fuel filter snapped. Subsequent replacement emergency replacement hose and bike didn't pick up revs. So suspect some debris in the carb. (That's the clean version, was thinking more horse manure!).

Daughter's boyfriend dismantled and cleaned carb. Bike will now idle ok. However, does not rev correctly and will not pick up to be ridden (ok, will do about 5mph but that's all).

It's almost like the throttle doesn't wind round far enough. Have checked what I can of the points (yes, it has points, it's that old). These seem ok but I know this was one bit replaced as part of the tlc.

So, in summary, any help/advice/pointers appreciated for a non-reving old CG125. Thanks in anticipation.

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Last edited by map on 23:03 - 17 Oct 2010; edited 2 times in total
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Mr Calendar



Joined: 14 Jun 2004
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PostPosted: 20:10 - 09 Oct 2010    Post subject: Reply with quote
rob yarrr wrote:
hows the air filter and plug ?

Thanks for the quick reply.
Brand new out of the bag/box air filter and plug.
Can give update on plug colour tomorrow if required,
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Gibbs, what did Duckie look like when he was younger? Very Happy
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Mr Calendar



Joined: 14 Jun 2004
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PostPosted: 20:15 - 09 Oct 2010    Post subject: Reply with quote
rob yarrr wrote:
yerr might aswell...check the chokes not on

Done.
Bike will start with choke on half and idle on off now.

By off I mean all the way to the top.
This closes the valve in the carb.
Choke all the way down, valve full open in carb.

HTH Thumbs Up
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...and the whirlwind is in the thorn trees, it's hard for thee to kick against the pricks...
Gibbs, what did Duckie look like when he was younger? Very Happy
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Mr Calendar



Joined: 14 Jun 2004
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PostPosted: 20:45 - 09 Oct 2010    Post subject: Reply with quote
rob yarrr wrote:
Hmm just guessing here really ...
maybe the main jets blocked up but the pilot is clean

Would have been my first guess as well, however...
map wrote:
...Daughter's boyfriend dismantled and cleaned carb...
Guy was quite thorough.
We also blaster carb cleaner through air intake with engine idling. Made no improvement.
Plans for tomorrow are to take carb off again and marinade in petrol to make sure cleaned.

I'll try and find air compressor to make sure jets clear. Visually look ok.

Done a google and scared myself as one US site thinks maybe poor compression etc. Really don't want to take the head and cylinder apart atm if I can avoid it.

HTH Thumbs Up
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Gibbs, what did Duckie look like when he was younger? Very Happy
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Mr Calendar



Joined: 14 Jun 2004
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PostPosted: 22:14 - 09 Oct 2010    Post subject: Reply with quote
rob yarrr wrote:
yerr but if theres general crap in the tank it would have just been sucked through and blocked it again

Fair point well made.
However, forgot to mention new in-line fuel filter fitted as replacement for broken one.

I suspect original hose not right length so put strain on fuel filter connector which snapped.
So, with new filter doing best to keep crap out of the carb.

Any other advice or pointers welcome.

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Gibbs, what did Duckie look like when he was younger? Very Happy
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Mr Calendar



Joined: 14 Jun 2004
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PostPosted: 22:31 - 09 Oct 2010    Post subject: Reply with quote
rob yarrr wrote:
...there's a filter in the tap anyway,you could try running it without the filter on and just a pipe straight from the tank to the carb

Originally bike running ok with fuel filter. Put on replacement hose without filter (because it broke) and bike then had problems.

Had tap and filter out of the tank, cleaned and replaced. Refitted with in-line filter. Fuel flows ok from tank to carb. (carb. has drain screw).

So, I think the new fuel filter is a red herring. As said, symptoms are like not enough throttle can be applied. I agree the main jet could still be blocked but believe it's clear so looking for other possible causes.

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Gibbs, what did Duckie look like when he was younger? Very Happy
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Noxious89123
World Chat Champion



Joined: 10 Jun 2007
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PostPosted: 23:03 - 09 Oct 2010    Post subject: Reply with quote
map wrote:
As said, symptoms are like not enough throttle can be applied.

It's a long shot, but what's the throttle cable slack like? Did you slacken it right off to remove the carb?
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Blue_SV650S
World Chat Champion



Joined: 27 Nov 2008
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PostPosted: 08:57 - 10 Oct 2010    Post subject: Reply with quote
Its a blocked main jet*/emulsion tube. Some residue rubbish has found its way into the carb.



*or even sounds like he forgot to re-connect the throttle cable!
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Mr Calendar



Joined: 14 Jun 2004
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PostPosted: 23:02 - 17 Oct 2010    Post subject: Reply with quote
Quick update.
Problem appears to be sorted.

Issue 1 was the carb needed another strip down and clear.
Daughter's boyfriend's father came over and sorted.
Guy is used to sorting this kind of thing.

Issue 2 that he spotted and sorted was magneto cover not fully on.
Removal showed some damage to woodruff key.
This has caused slipping and so altered the timing.

No wonder didn't rev correctly.

Temporary woodruff key fabricated (guy is a fabricator by trade!).
Slotted all together and all appeared to work ok.
Getting a genuine woodruff key as this will be of hardened metal and when fitted this will complete the job.

Will give the CG some more TLC over the coming months.

Thanks to everyone for their advice.
If anyone has similar issues I hope this thread will be of some help.

Thumbs Up
____________________
...and the whirlwind is in the thorn trees, it's hard for thee to kick against the pricks...
Gibbs, what did Duckie look like when he was younger? Very Happy

Last edited by map on 09:27 - 18 Oct 2010; edited 1 time in total
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 01:50 - 18 Oct 2010    Post subject: Reply with quote
map wrote:

Getting a genuine woodruff key as this will be of hardened metal and when fitted this will complete the job.


Although if it's on in the right place now, the key is pretty superfluous. All the key does is make sure you locate the rotor in the correct place on the shaft when you fit it. It's the taper on the shaft that actually holds it in place. If it's on properly, what the key is made of is irrelevant (in fact, you could fit it without the key, it's just a bastard to get in exactly the right place).

If it's not on properly, it'll spin up and mangle the key even if it's a genuine one.

So, if it's fitted correctly with the tapers thoroughly degreased, the bolt torqued down on top of the rotor and is running properly, I'd leave it well enough alone. By all means get a new key and keep it somewhere safe to replace if you take the rotor off again but I see no good reason to strip it all down again now.
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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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Blue_SV650S
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Joined: 27 Nov 2008
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PostPosted: 18:21 - 18 Oct 2010    Post subject: Reply with quote
Yep, as stinky said, not worth replacing the key as it has already done its job*!! Thumbs Up



*orientating the flywheel
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