Bogging down/ rough running problem

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Matt Hale
Posts: 75
Joined: 08 Oct 2020 10:00
Location: London

Bogging down/ rough running problem

Post by Matt Hale »

Hi All- I have searched the forum to try to avoid writing this post but cant quite find anything covering it but if there is please send me there....

The problem is that despite easy starting and bike ticking over OK ~(ish) when I open the throttle beyond the first 5th or so, especially quickly, it bogs down/runs rough. Up hill it is worse. If I back off in most circumstances it improves and in fact it will increase in revs. The symptoms are quite extreme and it is hard to pull away smoothly from lights and overtaking is not possible.
I have tried adjusting mixture screws and lowered needles and now gothic back in teh middle setting. Nothing seems to make much difference. The air filters are currently out as another try- rubbers and box still attached. Spark plugs look sooty but only checked once stopped- I've not cut engine at speed and checked.

Q: Does this sound like a carb issue? (over rich mixture perhaps) or an ignition issue? (timing too advanced/too retarded) I also wonder if tight valve gaps might cause this. I did adjust and thought they were correct but maybe they are tight. I will be checking them again today (Sunday 21-8-22)
I realise there are many possible causes but if you have ideas of most common causes please let me know.
Many thanks in advance
Matt
350 Sport 1979 electric start model (missing)
Curry yellow tank etc paint work, navy blue frame, silver wheels.
3potjohn
Posts: 1243
Joined: 02 Jun 2007 13:58
Location: Devon

Re: Bogging down/ rough running problem

Post by 3potjohn »

Make certain that the “chokes” tips are not perished.
What jets etc are you running? Any if them loose? With the float bowls off and a manual tap on as needed check that fuel flow is stopped when you lift the float.
John
Matt Hale
Posts: 75
Joined: 08 Oct 2020 10:00
Location: London

Re: Bogging down/ rough running problem

Post by Matt Hale »

Many thanks John. I put new chokes on quite recently and so I think they are OK. I’ll def check fuel stops when I lift the float. I do wonder if float height correct but I always find it a bit hard to know exactly where to measure but I’ll make an effort and do that. I’m running 43 pilots. Standard others. Not sure of size but they’ve been in ages but have cleaned all and checked clear tunnels in carbs in float bowls.
I changed the plugs’s today to pin head ones and weakened the mixture. Before that I found front plug was sooty/slightly oily…After plug change things improved a bit but I just rode 8 miles in London traffic and by end the stuttering had returned. Ran better at start of journey when engine cooler. BTW- I’ve checked the valve gaps and they are spot on. The bike also starts easily…but idle not achieved yet with new weaker settings but might be possible.
Could it be timing is out ? I’ve not strobed it and wonder if it’s advanced a touch? Would that cause obvious issues fairly quickly after riding?
350 Sport 1979 electric start model (missing)
Curry yellow tank etc paint work, navy blue frame, silver wheels.
julianharty
Posts: 478
Joined: 15 May 2016 16:34
Location: High Wycombe
Location: High Wycombe Area (Bucks)

Re: Bogging down/ rough running problem

Post by julianharty »

Matt,
I had a similar behaviour on my Kanguro X, but not as extreme as you've had. Mine would eventually 'clear' and rev out particularly if I let it build the revs gently. The exhaust was very sooty, and so on. And if I rode it at slow speed for a while (as I had to at an event in late June then the behaviour became much much worse with the bike refusing to rev properly).

I did three things that helped overall, at least the first two may well help you.
  • I fitted brand new needles, E17's, bought from stein-dinse in Germany. I'd actually bought these for my Sport as both models have the same needles, however as I'd bought 2 sets to compensate for their shipping charges I had an 'extra' set.
  • I reduced the pilot jets from 50's to roughly 44's. I'd bought a set of pilot jets from 40 - 49 from kmt products so actually fitted 1 size different jets, a 44 and a 45, here's a link to the set of pilot jets I use https://www.kmtproducts.co.uk/?cat=DELL ... egory_id=9
  • I subsequently reduced the main jets from 108 to 102 (this size isn't going to be the correct set for a Sport)
I've since reduced the pilot jets to 42's as I ordered another range of pilot jets from kmt products to suit which has helped crisp up the acceleration.

So, my suggestion given you've already reduced the pilot jets is to try and obtain a set of E17's. Stein-dinse also sell the 260BD atomisers and again I'd bought a set for my Sport to go with the E17's (My Kanguro has a different atomiser that's not available as far as I can tell).

FYI I've added the order lines I made for the jets with Stein-dinse in the hope that'll make them easier for you to find on their website. Delivery was 10.90 € to the UK and they arrived without any import or customs delays or issues within a week.
  • 4 x Dellorto Zerstäuber 260 BD, VHBZ
    Delivery time 1-3 working days
    Carburettor spare part: 9994-260
    6,31 € 25,24 €
  • 4 x Dellorto Needle E 17 VHBZ-PHSA
    Delivery time 1-3 working days
    Carburettor spare part: 2343-17
    6,35 € 25,40 €
PS: I'd already replaced the choke assembly with new spares ordered from EuroCarb (who are very helpful but don't have some of the items stein-dinse have and vice-versa).
norbert
Posts: 750
Joined: 15 May 2007 15:15
Location: Lübeck/Germany

Re: Bogging down/ rough running problem

Post by norbert »

For me it makes no sense trying to carburate before you are sure about the exact ignition timing.
BumbleBee
Posts: 140
Joined: 13 Jun 2017 21:10
Location: Reading

Re: Bogging down/ rough running problem

Post by BumbleBee »

Sometimes the following can cause symptoms like you describe, as they cause the ignition timing to fire earier and later than the setting in a random way.
1. Center of pickup rotor gets loose in the rotor.
2. Woodruff key on camshaft belt pulley wears.
3. Cam belt wears beyond the allowable slack.

Sadly we have experienced all of the above, happily they are all easy to fix.
G&A
Matt Hale
Posts: 75
Joined: 08 Oct 2020 10:00
Location: London

Re: Bogging down/ rough running problem

Post by Matt Hale »

I’m going to check all these things before buying more carb parts as in past the current carb settings and parts have worked. Timing should be checked anyway and I’ve never checked the woodruff key. Belt replaced not very long ago but perhaps wrong size? I’ll check that…if all that is ok I’ll spend on the carbs. I have needles size E17 now but maybe worn…I’ll let you know how I get on…
Many thanks again all!
350 Sport 1979 electric start model (missing)
Curry yellow tank etc paint work, navy blue frame, silver wheels.
BumbleBee
Posts: 140
Joined: 13 Jun 2017 21:10
Location: Reading

Re: Bogging down/ rough running problem

Post by BumbleBee »

If you let the bike tick over and put a strobe on the timing marks while it is doing so, and the timing dances around the mark, that could be the things I mentioned above. Good luck whatever it turns out to be.
mbmm350s
Posts: 666
Joined: 22 Jun 2018 10:18
Location: Reading UK
Location: Berkshire UK

Re: Bogging down/ rough running problem

Post by mbmm350s »

Hi Matt
The problem is that despite easy starting and bike ticking over OK ~(ish) when I open the throttle beyond the first 5th or so, especially quickly, it bogs down/runs rough. Up hill it is worse. If I back off in most circumstances it improves and in fact it will increase in revs. The symptoms are quite extreme and it is hard to pull away smoothly from lights and overtaking is not possible.
I agree with Norbert and Bumblebee here.

These are extreme problems, so the ignition timing and operation needs to be confirmed.

Firstly is this a new fault? Or has been getting worse?
Are both plugs sooty and or oily or just front?
oily implies worn rings but petrol especially in exhaust implies broken ignition or flooding

When a throttle is opened quickly then the engine pressure is increased,
Increased engine pressure requires higher spark voltage, if the spark is weak or at the wrong time, ignition will be killed.
Unfortunately its not always obvious from strobing because the engine isn't under load.
But here you can notice erratic behaviour or advance problems.
Spark plugs shouldn't be black on the electrode or nose.

Minor tinkerings with jets are probably not solving the fundamental issue.
If you can't overtake then either you are in too high gear for the revs or there is a serious fault.
Sometimes there is a bit of a hole with Sports , but drop a gear and away you go.
Never a hole on A Stradas or K stradas

I am running a standard Sport, with standard airbox and exhaust,
with New carbs on standard jets except pilot which is 48.

As for float height I road 30 miles a week ago with the float jet unscrewed
and hence not sealing on a 350 and despite being a bit fluffy it was running ok.
Float height adjustment isn't super critical.
If way too high might make idling overly rich and affect initial throttle opening.

Look for badly worn slides.
Carb balance is quite critical for smoothness.
Spark plugs BP7ES or equivalent work fine, no need for fancy plugs on standard bikes
Don't overtighten valve gaps must not be less than 0.1mm on PMS marks

all the best
Mark
Matt Hale
Posts: 75
Joined: 08 Oct 2020 10:00
Location: London

Re: Bogging down/ rough running problem

Post by Matt Hale »

Many thanks again!! I’ll def look at woodruff key and belt. I feel it’s electric issue and timing or spark occuring at wrong time or intermittently. Really appreciate the time you all spend on writing detailed replies. All useful and just have to decide which order to try them!
Best - Matt
350 Sport 1979 electric start model (missing)
Curry yellow tank etc paint work, navy blue frame, silver wheels.
Matt Hale
Posts: 75
Joined: 08 Oct 2020 10:00
Location: London

Re: Bogging down/ rough running problem

Post by Matt Hale »

Hi All- My current situation with this 'problem' is that the bike starts an runs beautifully and then after about two miles or less depending, I think, on temperature I=the bike begins to stutter /falter and not rev smoothly especially if I open throttle fast- in low or high gear. I have checked the tappet gaps and they are 0.10mm when cold. I wondered if they were too tight and getting even tighter when hot but unless that gap is wrong then it can't be them.
What gets hot and then cause this kind of symptom? Any ideas VERY gratefully received...
Thanks again...
350 Sport 1979 electric start model (missing)
Curry yellow tank etc paint work, navy blue frame, silver wheels.
MickeyMoto
Posts: 2415
Joined: 22 Nov 2008 17:41
Location: Even further oop North

Re: Bogging down/ rough running problem

Post by MickeyMoto »

Magneto coil breaking down?
Matt Hale
Posts: 75
Joined: 08 Oct 2020 10:00
Location: London

Re: Bogging down/ rough running problem

Post by Matt Hale »

Thanks Mickey. I’ll try to check it…
350 Sport 1979 electric start model (missing)
Curry yellow tank etc paint work, navy blue frame, silver wheels.
mbmm350s
Posts: 666
Joined: 22 Jun 2018 10:18
Location: Reading UK
Location: Berkshire UK

Re: Bogging down/ rough running problem

Post by mbmm350s »

To Add to what Mike says.

If there is a misfire when hot it could be a fault with the pickup unit if you have the standard one that is. Here there could be very fine hairline crack(s) in the resin, particularly near the visible core pieces. I use some talc or similar to make them more visible.
The very fine wire that is used can be broken, but sufficient contact is there when the engine is cold for it to work, as the temperature increases then the crack may open and the contact not so good.

While you are in the pickup area do check that the rotor isn't falling apart as previously mentioned by Bumblebee in point 1.
and check that the soldered connections to the pickup itself are good.

Do not overtighten the pickup screws as this can cause distortion of the plastic and make unit more prone to cracking.
Please refer also to the parts book for the correct special cupped washer on the rotor nut and the large o.d. washers to be used on the pickup screws.

Cheers
Mark
Matt Hale
Posts: 75
Joined: 08 Oct 2020 10:00
Location: London

Re: Bogging down/ rough running problem

Post by Matt Hale »

Many thanks Mark- I will examine carefully. Presumably if there are cracks in the resin of the pickup I will need to get a replacement from Marcus Heilig ?<mheilig@freenet.de>. The Alternator magneto stator Coil....I had one coil rewound- the single small one...but just found this for sale- maybe I should replace with this I have found on eBay anyway as so cheap but not sure it would fit/be correct replacement?..."Alternator stator for Morini engines 84mm mtp-racing GmbH" ...<https://www.ebay.co.uk/itm/363043707460 ... 7cEALw_wcB> ?
Last edited by Matt Hale on 07 Sep 2022 13:20, edited 1 time in total.
350 Sport 1979 electric start model (missing)
Curry yellow tank etc paint work, navy blue frame, silver wheels.
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