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Author Topic: CB210T "Stuttering" problem  (Read 734 times)

Offline Camaromuscle

  • Posts: 15
CB210T "Stuttering" problem
« on: Apr 30, 2017, 08:07:33 »
Hi,

I have a 1981 Honda CB125T with a 210cc bigbore kit.
I am having some "stuttering" problems when i ride the bike, and it gets worse when the bike gets warmer.
If i ride downhill and "force" the bike past the stuttering it is ok, but if i ride uphill and the engine is under load it will just keep stutter.
It idles fine, the problem only occurs during 3/4 throttle and under load.

Little history: I did not ride the bike that much with original airfilters and exhaust, therefore i do not know if the problem was present then as well.
I have 2 original keihin PD26 carburetors with UNI pod filters.
Also before i installed the big bore kit i had this problem, and i did some experiments with pipes between the airfilter and carburetor, which helped a little bit.
the original airbox is damaged and thrown away so i cant test with that.

With 125cc i had 95 main jets, now i have 110, and i have synchronized the carbs with a vacuum gauge.


Could this be my timing, valve gaps or is it most likely carburetor related?




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« Last Edit: Apr 30, 2017, 08:20:11 by Camaromuscle »

Offline interceptor

  • Posts: 865
Re: CB210T "Stuttering" problem
« Reply #1 on: Apr 30, 2017, 17:31:51 »
Do you think that maybe it could it be the clutch?
Opinions are like farts... they stink and no one wants to hear it except yourself.

Offline Camaromuscle

  • Posts: 15
Re: CB210T "Stuttering" problem
« Reply #2 on: May 01, 2017, 06:17:47 »
I forgot to mention that the clutch is rebuilt recently, and i think i would felt a more mechanical stuttering if it was the clutch?

Offline interceptor

  • Posts: 865
Re: CB210T "Stuttering" problem
« Reply #3 on: May 01, 2017, 07:01:31 »
I am not an expert in any capacity, but I think the stuttering would not go away at any speed if it were a lack of fuel (jets), it would continue throughout the whole range.  Getting worse as it warms up seems like something else other than fuel related to me.  Have you looked at the spark plugs?
Opinions are like farts... they stink and no one wants to hear it except yourself.

Offline TheCoffeeGuy

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Re: CB210T "Stuttering" problem
« Reply #4 on: May 01, 2017, 08:53:49 »
I would check your timing chain tension.
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Offline Camaromuscle

  • Posts: 15
Re: CB210T "Stuttering" problem
« Reply #5 on: May 01, 2017, 15:21:36 »
The spark plugs have a good white/brown colour.
I checked the timing chain today, and that was ok.

i checked the ignition timing and the right cylinder is firing a little late?

I have now ordered new circuit breakers, and will try to align everything better.

Online Sonreir™

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Re: CB210T "Stuttering" problem
« Reply #6 on: May 01, 2017, 15:41:21 »
The problem getting worse as the engine warms is a bit telling.

Sounds like you might be running lean.

Try some larger jets and see how things go.
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Offline Camaromuscle

  • Posts: 15
Re: CB210T "Stuttering" problem
« Reply #7 on: May 03, 2017, 12:57:36 »
I have actually bought genuine OKO flatslide carbs now, as i am tired of the stock ones.
Hope it will help with the correct jetting.

Offline interceptor

  • Posts: 865
Re: CB210T "Stuttering" problem
« Reply #8 on: May 06, 2017, 09:01:09 »
Sweet!  Did you order some new (bigger) jets, too?
Opinions are like farts... they stink and no one wants to hear it except yourself.

Offline Camaromuscle

  • Posts: 15
Re: CB210T "Stuttering" problem
« Reply #9 on: May 06, 2017, 11:20:48 »
Yes i did, but now i have a new problem:

I was just going to check my ignition timing, but when i measure the left side contact breaker i always get 12v when i turn the motor?
I have adjusted the gaps on both contact breakers, and the right is ok (goes on and off as it should)

Wht could be the fault with the left side?

Offline interceptor

  • Posts: 865
Re: CB210T "Stuttering" problem
« Reply #10 on: May 06, 2017, 13:16:31 »
Did you install new points?  The reason I ask is that I did that one time, and I seem to remember this happening to me.  I think there was a very small nylon washer I didn't install, or installed improperly, so it was grounding out all the time?  Something like that.  Good luck :)
Opinions are like farts... they stink and no one wants to hear it except yourself.

Online Sonreir™

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Re: CB210T "Stuttering" problem
« Reply #11 on: May 09, 2017, 14:08:39 »
Did you install new points?  The reason I ask is that I did that one time, and I seem to remember this happening to me.  I think there was a very small nylon washer I didn't install, or installed improperly, so it was grounding out all the time?  Something like that.  Good luck :)

Been there, done that. It's sort of a rite of passage. ;D
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Offline Camaromuscle

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Re: CB210T "Stuttering" problem
« Reply #12 on: May 09, 2017, 17:16:48 »
How should i check this? The points were brand new and was complete like this:
http://www.wemoto.com/parts/picture/hl-181183/

Online Sonreir™

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Re: CB210T "Stuttering" problem
« Reply #13 on: May 09, 2017, 17:34:40 »
Rotate the crankshaft until the points are open. Using a multimeter, test the resistance between the two sides of the points. You should get an Open Line.

Next, measure the resistance between the stationary side of the points and ground. You should get a reading very close to zero Ohms.
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Offline Camaromuscle

  • Posts: 15
Re: CB210T "Stuttering" problem
« Reply #14 on: May 13, 2017, 08:22:29 »
Hi, i measure 5,3 ohms between the points when they are open, and from stationary to ground 0,2 ohms.

I have a battery eliminator and rectifier from oregon motorcycleparts installed. Maybe it should be like this with this kit?

The spark is weak with the eliminator kit, but with a battery it is good.

I do not think the battery eliminator is broken, but maybe my stator is not good enough. This was originally a 6v bike, and i have changed everything to 12v, but the stator is original.
I rode the bike last year with this setup and no problems, the stator could output more than 12v.

Online Sonreir™

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Re: CB210T "Stuttering" problem
« Reply #15 on: May 13, 2017, 15:38:23 »
You have a combination of problems, it seems.

You should not be able to get a reading between the points when they're open, so that's problem number one.
Problem number two is the battery eliminator. They rarely work on the Honda twins since the alternator is so anemic.
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Offline Camaromuscle

  • Posts: 15
Re: CB210T "Stuttering" problem
« Reply #16 on: Jul 31, 2017, 13:00:07 »
I still have the same problem, and i will take the bike out for a test ride tomorrow to troubleshoot the problem.
Things i am going to check:

- plug chop when the bike stutters
- try riding without the air filters
- try riding with choke on

The carbs are synced, ignition is timed correctly (just stationary), valves are set, the ignition colour is checked with colortune and the colour of the combustion is ok. I have recently changed to oko flatslide carbs, still the same problem.

What else should i check?
The main keyword i think in this troubleshooting is that it is ok when cold, but gets worse the warmer the engine gets?

I may also try to bypass the condenser/battery eliminator tomorrow with a battery, just to check if the battery eliminator is not giving a good enough spark.

Offline teazer

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Re: CB210T "Stuttering" problem
« Reply #17 on: Jul 31, 2017, 13:26:55 »
If it gets worse when it heats up, the jets are too big - it's rich.

With points open there should be zero connectivity.  Is it possible that the condenser is wired to the stationary point instead of the moving one?  That's one of many common mistakes when replacing points.  There is a correct sequence to assembly.

A stock small carb on a larger motor will usually go rich because the pressure drop across the jets is much higher, so you may need stock or smaller main jets. It's also possible that the needle taper is now wrong for your motor, but one thing at a time. Get the ignition right first.

Yu might also want to check plug caps for resistance.  They deteriorate.

Offline Camaromuscle

  • Posts: 15
Re: CB210T "Stuttering" problem
« Reply #18 on: Jul 31, 2017, 13:47:39 »
Hi teazer and thank you for your answer.

Since the bike stutters at 3/4 throttle i will try to drop the needles before my testride tomorrow to lean it out.

I think the points measurement problem from earlier in this thread was just my blunder, i did get to measure the points eventually. I have never touched the condenser for the ignition and i believe it is wired correctly, i will recheck it though.

I bought the oko carb from midatlantic trails, the guy who works there is really helpfull with all troubleshooting and he reccomended the 26mm carbs for my bike, (26mm was installed originally as well).
I can try smaller jets, but maybe drop the needle first?

The plug caps are new (bought new coils, wires and ngk plug caps with resistors last year.)
But the caps can be bad or fake ngk? I have a set of  ew red ngk caps that i can try.