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Post by milly on Apr 26, 2018 14:31:50 GMT -5
I have 2 139qmb engines the same year 2005 both running ok but both hate starting on electric start. One has a new starter. Both turn over fine clean carbs, valves ok compression good. Start kick fine, new Naraku cdi units on both and new plugs just wondering if this is a common problem or am I missing something. Both usually start ok when hot.
One is on vacuum tap other is on normal fuel tap.
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Post by scootnewb on Apr 26, 2018 15:03:31 GMT -5
bump.
I would like to know too. My 139qmb does not like starting if it is cold out and requires a ton of start button pushes, lots of throttle and a few kick starts. If it is say 50F out, touch the button once and all good.
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Post by KSR Moto on Apr 26, 2018 15:04:28 GMT -5
I belive that your starting issue lies within the cdi, try putting back original cdi
Performance cdi's advance ignition too much and cause hard starting
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Post by KSR Moto on Apr 26, 2018 15:06:46 GMT -5
bump. I would like to know too. My 139qmb does not like starting if it is cold out and requires a ton of start button pushes, lots of throttle and a few kick starts. If it is say 50F out, touch the button once and all good. Replace automatic enricher |
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Post by scootnewb on Apr 26, 2018 15:19:29 GMT -5
bump. I would like to know too. My 139qmb does not like starting if it is cold out and requires a ton of start button pushes, lots of throttle and a few kick starts. If it is say 50F out, touch the button once and all good. Replace automatic enricher True. I have a replacement Keihin on the way. However, the carb in there now is only a month or so old. Dang, I completely missed that but remember reading/hearing about that. |
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Post by cagiva4ever on Apr 26, 2018 16:15:41 GMT -5
Not all 139QMB CVK automatic chokes are the same.... some have adjustable Needle.... some needle profiles also varie...Some have different pinout on the 2-wires.
with the adjustable needle version its possible to prolong the activity Duration by 1-minute, iirc....
Depends also about the cdi ign curve... that with poor Auto-choke and not using Accelerator pump(ing) only makes Starting harder..and Fuel mixture "pearl" dropleting to cold metal surfaces...
cold sparg plug and possibly poor ht-lead etc ign issues. Poor Vacuum at cold engine.. idle circuit jetting... it all TopsUp 2gether....
BTW, does any1 happen to have photos/link about the "Conversion kit manual Choke" for 139qmb CVK ?
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Post by milly on Apr 26, 2018 17:20:39 GMT -5
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Post by GrumpyUnk on Apr 27, 2018 12:18:22 GMT -5
I will suggest that if the carburetor is adjusted for a good smooth idle at 1500-1900rpm(I understand the suggested numbers vary), then it should start pretty quickly using the electric starter motor.
If you think it is running too lean to start, a few twists of the throttle should squirt a dollop of fuel directly into the venturi to enable vaporization and combustion.
Fresh fuel is better than any fuel that has had time for the lighter, easier to get burning components to vaporize and waft away.
I think the kick start will start a more reluctant engine where sometimes the electric start will not. When checking compression, better & higher numbers are achieved by using the kick starter. It apparently whips the crankshaft around quicker, more compression == easier start.
It might be worth while to check the compression on engines that are hard to start. I have found that numbers in the 110-120 range seem a bit marginal in their desire to run, but it may have been the plugged pilot jets or the mal-adjusted idle speed & mixture.
In general, if the idle is good, they are more likely to want to start & run, no hand throttle needed.
tom
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Post by tocoo on May 1, 2018 1:41:44 GMT -5
check that the needle of the auto-enricher is not so long that it would block the enriching circuit even when cold. The easiest way to check this is to remove the auto-enricher and put it side by side with the carb to see if the needle reached the bottom of the circuit.
you can also play with the depth of the enricher once it is mounted, by unplugging it by 1mmwhen you try to start.
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Post by tocoo on May 1, 2018 1:51:36 GMT -5
Not all 139QMB CVK automatic chokes are the same.... some have adjustable Needle.... some needle profiles also varie...Some have different pinout on the 2-wires. with the adjustable needle version its possible to prolong the activity Duration by 1-minute, iirc.... Depends also about the cdi ign curve... that with poor Auto-choke and not using Accelerator pump(ing) only makes Starting harder..and Fuel mixture "pearl" dropleting to cold metal surfaces... cold sparg plug and possibly poor ht-lead etc ign issues. Poor Vacuum at cold engine.. idle circuit jetting... it all TopsUp 2gether.... BTW, does any1 happen to have photos/link about the "Conversion kit manual Choke" for 139qmb CVK ? I want also to convert my auto-enricher into a manual choke but for cheap. I wanted to start a thread about this, but since I do not have received the manual cable, you can start one already. The only thread I have found is this sobisource.com/gy6-manual-choke-conversion/and an alternative method here symforum.com/index.php?PHPSESSID=11598dddfdbb1c0f70fb588236ddff88&topic=1673.msg9861#msg9861 I found this part but I do not know if it would be useful www.pedparts.co.uk/product/286/manual-choke-u-clip-type-conversion |
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Post by cagiva4ever on May 1, 2018 7:53:48 GMT -5
i have had same idea, a DIY version, since having a hunch that Commercial version is rare and expensive...like "Milly" posted ordering it from States...
iirc, i have old notes about seeing that dellorto phva moped choke bein used on some cvk's... maybe i refind it web post.... if it fits i wonder how it has worked as NOT having a needle, makes it most likely Uber rich.....
Hence i havent bothered personally even test fitting it, as i do have 2~3 of them genuine dellorto phva carbs and lever chokes from Derbi Senda's etc....i do have Aerox engine assy too and its Carb with cable choke....
anyway, looks like diy modding Stock e-choke is the right way to go now.
i had an same simple idea of using more flexible bicycle/moped cable, spring and Flux soldering the cable nipple to the Brass plunger....the basic construction...
and when i make it , i make 2 and for the 2nd i re-profile the needle....
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