Hi everyone

norn

New Member
Hey guys and girls, I'm a 23 year old Ace 125 owner in Albany, Western Australia, Australia. Aprox. 10 000 km on the clock. Long time reader (I was inspired to buy one originally when reading the "Bike in a box" thread), thought I'd finally make an account.

I'm currently just an owner and unfortunately not a rider. After having it hotwired, stolen, recovered, and completing numerous electrical repairs, I thought I finally had it sorted. Then, as I was exiting a freeway (travelling approx 80 km/h) and slowing down in the slip lane, it suddenly lost power and stalled. Plenty of fuel, petcock fine, so I tried starting it a ~50 times, but not so much as a whimper. I do the walk of shame the rest of the way to work, and then all the way home in the evening.

Eventually I muster the courage to start trying to fix it. Cleaned the carby, checked the air box, running fine, and idling! Very proud of myself. Take it out, get up to 80, and then the same power loss again, except it doesn't quite stall and I'm able to limp it home. I let go of the throttle and it stalls.

I replaced the carby with another fake Mikuni. Running fine, and idling, again! Exact same thing happens again when taken up to speed.

Took off the exhaust this afternoon to check for wasps nests, no problems that I can see. Ran it with the exhaust disconnected for a while, seemed happy at first, but then black smoke and a stall.

Am I missing something obvious? Is there something I should be checking?

Thanks for reading,

norn
 

stroker crazy

crazy as a fox
Got my thinking-cap on but haven't been struck by a brilliant solution yet!

Does it continue to run if you don't go over 60-70?

(It's not a good idea to run it without the exhaust)

Crazy
 

norn

New Member
Thanks for your mental energy, crazy!

I didn't quite explain myself properly. When I get the revs up high, then it's as if a switch is flicked that stops it from running correctly, and it won't be able to idle etc. The way to "unflick" the switch seems to be to completely dismantle and clean the carby, or replace it, at which point it will seem to work properly until it's revved high again.

(I put the exhaust back on :) )

norn
 

stroker crazy

crazy as a fox
Next time you take it for a ride take a plug spanner with you.

Pull the spark plug immediately after it dies to see if it oily or dry or whatever. What sort of plug are you using?

Double check the electrics for good earths, no shorts etc.

Crazy
 

r4g5

Member
Does it happen when the engine is hot and cold? I'm just wondering if it's revs or heat? I've been doing my valve clearances (with the help of crazy) recently so it's on my mind. If there is little/no valve clearance then it could affect performance at higher revs on a hot engine.
My first thought though was needle jet getting stuck but if you changed the carb then guessing it can't be that...good luck
 

Racing Ruben

New Member
I once had a similar problem with a cg125. After riding it for a while it kept on stalling. It was the fuel tank that sucked itself vacuum so the fuel stopped going to the carb. Maybe a long shot....
Good luck
 

stroker crazy

crazy as a fox
Racing Ruben said:
It was the fuel tank that sucked itself vacuum so the fuel stopped going to the carb …
Could be!

A lot of 'Ace' fuel caps leak - maybe this one seals too well.

Crazy
 

norn

New Member
Thanks so much for all the advice guys!

Crazy:
Next time you take it for a ride take a plug spanner with you.

Pull the spark plug immediately after it dies to see if it oily or dry or whatever. What sort of plug are you using?

Double check the electrics for good earths, no shorts etc.
Thanks Crazy, I'll do that. I'm using a stock plug, NGK, I think I'll buy a replacement and see if that helps. I really hope it's an electrical problem.

r4g5:
Does it happen when the engine is hot and cold? I'm just wondering if it's revs or heat?
Well, when I start it cold, it seems to be able to idle OK, but it starts creeping into a stall as it warms up (I thought this was to do with the idle screw, but you've got me thinking there may be more to this).
...but if you changed the carb then guessing it can't be that...
Yeah, I thought the same, but after changing that all over, I agree.

Racing Ruben:
It was the fuel tank that sucked itself vacuum so the fuel stopped going to the carb...
Thanks Ruben, no danger of that: when I refuel, I have to decide in advance how far I want to travel, and how tightly I want to be cornering (i.e. how much fuel I want to slop on my legs). A niiiiice loose "seal" for me.

EDIT: typo
 

r4g5

Member
I'd try opening the choke when it begins to stall and see if this has any effect...mine had running issues at temp, tried this. It ran better so I knew the mixture screw had to come out a bit. Would be weird that you're getting the same symptoms on two carbs though

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norn

New Member
r4g5 said:
I'd try opening the choke when it begins to stall and see if this has any effect...mine had running issues at temp, tried this. It ran better so I knew the mixture screw had to come out a bit. Would be weird that you're getting the same symptoms on two carbs though
Yeah, opening the choke near a stall keeps it alive. I'll try messing with the mixture.
 

2b

New Member
If you do start adjusting the carb take a look in here...
https://docs.google.com/spreadsheets/d/1USvziYIyzfyxfZA1YYpQf9eP4djb0GLWbvWcmME88Gk/edit#gid=1

Cheers
Richard
 

r4g5

Member
Also be careful that any carb adjustment isn't disguising some other issue...check out what crazy said. I know mine was a bit off cos I put a pod on it but waiting to rejet till I get the CDI and exhaust sorted

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norn

New Member
Thanks for all the tips guys, you've given me some great stuff to work through. I'll update you all on Monday, weather permitting.
 

Sneikz

Member
For my 2 cents worth, have you drained the tank. Sounds like fuel starvation and rest period allow carbie and fuel line to fill. I'd check the in-tank filter. A quick and easy check. It doesn't take much to starve an engine and given it appears to continue slightly under choke, this may be the problem. I'd remove the tank and decant from the filler via old stocking and flush.
 

orrible-64

Member
Sounds like a fuel issue. Still check what ignition module it has. Ok racing have a rev limiter. That would stop motor but you would be able to restart. My first ace used to stall on a long ride due to sticking valves. This went away as it wore in


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