128 replies to this topic

[Pict]

i've got news for all. it seems this is a common problem in this jind of bikes. i've been talk to other owners in portugal and i know just in my town at least 4 identical situations. when we press the starter one of the sparks goes nuts and the bike works just in one cilynder. the real question is - why? if we lift just a bit the spark plug she normalizes. WHY ????
Jesus i'm tired.

Just a crazy thought that the plug "reach" may be wrong - have you checked the plug type? Or it may be the gap is wrong? But it's odd that others may have the same problem - is it all reported to happen on the same side? Is it on the right hand side? Does it improve if the bike is level? Just thoughts.

[tdm850rider]

Could it be the sidestand lean? Gass 'flooding' the lower cylinder more than the high side?
Or the same type of thing with oil draining from the high side and collecting in the low side?

Old style BMW opposed twins did something like that but they were much higher/lower than vertical twin cyls.

Do any of you (who suffer this problem) have a center stand?
Try parking it overnight on that and see if it makes a difference.

[mechinha]

Just a crazy thought that the plug "reach" may be wrong - have you checked the plug type? Or it may be the gap is wrong? But it's odd that others may have the same problem - is it all reported to happen on the same side? Is it on the right hand side? Does it improve if the bike is level? Just thoughts.

i believe the mech. was aware of that problem. in other thought the problem seems to be "similar" but nt identical - i know it loks weird
mine is in the left hand side. a friend of mine has a similar problem inthe right side and another one had the same shiit problem in both of the plugs. i don't believe in witches bt the exist...i think!!

[mechinha]

Could it be the sidestand lean? Gass 'flooding' the lower cylinder more than the high side?
Or the same type of thing with oil draining from the high side and collecting in the low side?

Old style BMW opposed twins did something like that but they were much higher/lower than vertical twin cyls.

Do any of you (who suffer this problem) have a center stand?
Try parking it overnight on that and see if it makes a difference.

not a single soul has a center stand. in the matter of a gass flooding issue can you be more specific?? you see this problem only hapens when i ride more in town...could it be a low rpm problem and in an afirmative case, why? should i have to carry 20 extra sparks each time i ride the bike??

[sidestand]

Are you using the same grade of petrol as the rest of us then - in the UK we'll all be running on 95 octane

[mechinha]

Are you using the same grade of petrol as the rest of us then - in the UK we'll all be running on 95 octane

yes we all use the same fuel 95 octane

[tdm850rider]

in the matter of a gass flooding issue can you be more specific??
this problem only hapens when i ride more in town...

just gravity, there must be some fuel leakage when sitting or why would there even be an 'off' position in the fuel tap. It may be collecting more in the lower float bowl.
If it happens after low speed/low rpm town riding.... have you looked at the emulsion tubes (needle jets)?

Whats the milage on the bike?

[mechinha]

just gravity, there must be some fuel leakage when sitting or why would there even be an 'off' position in the fuel tap. It may be collecting more in the lower float bowl.
If it happens after low speed/low rpm town riding.... have you looked at the emulsion tubes (needle jets)?

Whats the milage on the bike?

they've have been replaced, but needles we dind't think it would be necessary. the bike only has 20.000 km . do you consider that we must had replaced the needles? a few days before she collapsed on me again, a weird fact happens but i didn't pay too much attention. i has trying the behavior in a high rpm let say 7000 rpm 180 km h, when suddenly she cut a bit and it seemed to fail the ascent. but only did this once i was able to achieve 210 khm and was ok. i've asked for help to a guy who worked in a spark factory showed him my sparks and this was his answer: Carbon accumulates on the insulator nose forming a leakage path to earth. The engine misfires resulting in bad starting and poor acceleration. Particularly common with unleaded fuel.
Causes:
- Too rich a fuel mixture
- Excessive use of choke
- Prolonged slow speed driving or idling
- Blocked air filter
- Spark plug heat range too cold

Edited by mechinha, 21 January 2008 - 03:52 pm.

[mechinha]

why would there even be an 'off' position in the fuel tap. It may be collecting more in the lower float bowl.

you mean when i stop the bike i should tourn the gas off?

[tdm850rider]

why would there even be an 'off' position in the fuel tap. It may be collecting more in the lower float bowl.

you mean when i stop the bike i should tourn the gas off?

You could try it and see if it makes a difference... Personally, I never turn mine to off (well, hardly ever).

Someone more knowledgeable may chime in but if it were me I would change the tubes and the needles...
they both wear out.

[mechinha]

hi people...does anyone have one or more suggestion?? the needles are fine they were measured with a new ones, the coils isolated with self amalgamating tape but yesterday did the same sh#*$t again. i believe that this has to be a electrical problem.. but something that happens only from time to time.. how does a starter relay behave? could it be?
thanks for listening me(i mean reading)

[TonyDevil]

starter relay, CDI or wiring
if it was starter relay you would get the occassional 'click click click' when you try to start it
CDI & wiring would be intermittent electrical issues until they die totally

suggest gettin a multimeter and poking it a bit on the wiring loom
sorry but its going to be time consuming and painful

[mechinha]

Can you take a picture of the spark plugs?

Will give us a good clue.

p.s. How a bout one of the needle valves not seating correctly now and again. If I remember correctly, they have a rubber sealing end which goes hard after a few years.

hi
ok i will ask to the fellow that is trying to solve it. you just want a photo of the spark plug, correct? about that rubber it's also a good suggestion. Meanwhile i've already contact the Portuguese Yamaha and they were not very elucidative.

i'll keep on touch (unfortunately on foot...buááá java script:add_smilie("","smid_38")
ahhhhh.gif)

[wicklamulla]

have you inspected/cleaned the sidestand cutout switch wiring and plugs as they can corrode ?

[mechinha]

have you inspected/cleaned the sidestand cutout switch wiring and plugs as they can corrode ?

sorry for so late answer but my pc has been "silenced" by a new virus but now I'm back again. the bike is at the mechanics but i will tell him to check that point.

[mechinha]

hi. untill so far nothing new. i keep doing the some sh#$t. even with a diferent spark (more expensive) it's samething.
does any of you wisdom guys has a photo related to fuel levels/float height and how can we make the correct measure, standar values etc... well i need all the information possible related. if you can help me.

cheers

[Ruairi]

have you inspected/cleaned the sidestand cutout switch wiring and plugs as they can corrode ?

Hey'ya Wicky,
Given that I've just been through the sidestand/electrical thang with my beast.....wouldn't sidestand issues cause complete enjun cut - not just single cylinder issues?

Hi Mechinha,
I could be soooo wrong but it sounds to me (not that I'd be an expert or even close! ) like the ignition system is only getting a spark to one cylinder - this only happens after riding for some time so the fault is intermittent; which means it could be that after some vibrations or heat build up the problem shows up. The electrical signal path from the battery/CDI to the coils, and all components in between, would be my first port of call with a multimeter.... it will take a while but it doesn't cost anything except time and if you find nothing at least you know that it is NOT an electrical problem.
Make sure you pull and drag at ALL connectors until you are 100% sure they are perfect. The wiring diagrams are available on JBX's "Pages of Wisdom" or I can send them to you.
I had to take my bike apart 7 times before I found that the sidestand switch was faulty, you will be surprised how quickly you begin to understand the diagrams...

Best of luck

[JBX]

I'd go for a carb issue, rather than an electrical problem.

As there is only one ignition circuit/coil on Mk1s, both cylinders receive the same spark at the same time (two sparks per engine cycle, one is a "lost" spark) so just swap ht wires / caps & plugs to check all's ok.

Then go for a complete carb check.

I read some times ago about a not well-known issue (amont all the other, well known issues) with Mikumi BDST38 : a small factory bore inside the body which is blanked with an o-ring (inside) and a cap (on top). As the o-ring gets old it starts to leak.

Hope it'll help !

[mechinha]

: a small factory bore inside the body which is blanked with an o-ring (inside) and a cap (on top). As the o-ring gets old it starts to leak.


Thank to you guys for keep trying to help me. i apologize but i am really a complete nerd in mechanic issues, so I'm forced to ask you if you could be more specific. for example in this sketch could you mark the o-ring place ( more or less)
thank you dudes..

http://i269.photobuc...a/Needlejet.jpg