View Full Version : Two-stroke plug lifetime?
stoo
21st September 2012, 08:46
Bike (RG150) needs a new plug every 100-150 k's, but otherwise runs sweet and starts in one or two kicks.
The plugs I pull out look like so:
270379
And work fine again for a while if I give them a bit of a scrub and gap check.
What's a likely cause for this in a 2stroke?
Manual says the oil pump is fine, but I spent ages trying to reproduce the carb tuning procedure from the manaul after I cleaned it.
Bike wouldn't play the game, but I eventually got it to roughly follow the rules and had it running/idling/starting nicely and thought I had it sorted.
sootie
21st September 2012, 09:05
Bike (RG150) needs a new plug every 100-150 k's, but otherwise runs sweet and starts in one or two kicks.
The plugs I pull out look like so:
270379
And work fine again for a while if I give them a bit of a scrub and gap check.
What's a likely cause for this in a 2stroke?
Manual says the oil pump is fine, but I spent ages trying to reproduce the carb tuning procedure from the manaul after I cleaned it.
Bike wouldn't play the game, but I eventually got it to roughly follow the rules and had it running/idling/starting nicely and thought I had it sorted.
All my experience with many 2-stroke engine plug problems has been too much oil being burnt.
It is always a problem ensuring adequate lubrication without getting plug fouling.
A cheap multimeter will often show a reading across the plug on ohms range. This absolutely confirms fouling, but an infinite reading does not rule out the plug, because it is required to operate reliably in higher pressures, and at much higher voltages.
I can not view your photo very clearly, but if the plug looks black & sootie (yes thats me!) it is probably either a mixture which is too rich, or more likely too much oil in the combustion chamber. (It sounds like you are already on to this.)
I would check the spark external to the engine in a darker environment. It should be a clearly blue colour (It may not be that bright). If it is pure white (like a sparkler) the gap energy is low (even if it is quite bright). This would probably be due to fouling, and exchanging to a new plug outside the bike would prove this. (Another less likely possibility is a weak or otherwise faulty ignition system.)
Hope this helps.
eelracing
22nd September 2012, 09:07
Your sparkplug is very wet and could be indicative of a lot of around town low rev stop start riding?
I don't mean to tell you to suck eggs but Two Strokes love a good caning and perform best at high revs.Keeps the plug dry too.
Try and avoid labouring the engine,so rev it out more through the gears,holding a lower gear/higher revs around town.
While it may not endear you to your fellow road users and pedestrians,who cares eh, just take the long way home.
FJRider
22nd September 2012, 09:23
Take it for a ride that distance on the open road/motorway at (or above) the speed limit. I bet the plug will be fine at the end. But carry a few spare plugs anyway ... easier to replace and clean them later anyway.
The joys of 2-strokes ... :lol:
paturoa
22nd September 2012, 09:34
You should get ~10 thousand ks out of a plug on a RG150 if it is running sweet and the bike is used for general road use.
It is always hard to tell, but they will foul really quickly when running too rich. Take it to someone who knows what they are doing, or even a reputable bike workshop.
Asher
22nd September 2012, 10:30
Looks to be running too rich but we don't know what sort riding you were doing before hand. Go do a plug chop and see what it looks like then
imdying
24th September 2012, 11:49
How many kms on the engine? When was the last time you refreshed the top end? Very easy and cheap to do before it goes bang. Afterwards, not so much. Two stroke maintenance is easy, just never neglect it... it's not a four stroke where the cam chain or whatever will rattle around for years before actually causing serious trouble.
ellipsis
24th September 2012, 12:50
...yes, if the cam chain on the RG is rattling around you certainly do have problems...
stoo
28th October 2012, 14:33
Finally had some time to look more closely.
Did the multimeter trick and it's definitely fouled, and I'm blaming my carb.
Pulled it off again, checked/cleaned jets, and now trying to set the float height but this has me confused:
272323
Where exactly does distance distance (A) start and finish?
I assumed it would either be red or yellow:
272326
Never really had to set float heights before so I'm confused.
sootie
29th October 2012, 08:04
Finally had some time to look more closely.
Did the multimeter trick and it's definitely fouled, and I'm blaming my carb..
I think you should check the carb jetting, float level, and lubrication levels of the bike & correct these and any other problems as necessary.
You might also like to consider an Irium or Platinum spark plug. They cost a bit nore, but they last longer, and they are great at reducing fouling problems.
[Try "spark plug" on Trademe under "Motorcycle Parts". You will have to check that you buy the right plug. :) :)
stoo
29th October 2012, 21:19
float level
But how?
None of the measurement options I've tried (see two of them in the previous post) are physically able to match the manual specs before the bendy tab comes into contact with the rest of the float hinge thingy.
As of now, the lowest I can get is 10 (manual says 8). And fucked if I can figure out where the manual says I'm supposed to measure from (also see previous post).
I'm fairly certain the jetting is standard, unsure on the oil pump but by eyeometer the smoke levels appear normal now.
Will also investigate tasty sparkplugs too, now that I've fouled all my spares.
sootie
30th October 2012, 08:13
But how?
None of the measurement options I've tried (see two of them in the previous post) are physically able to match the manual specs before the bendy tab comes into contact with the rest of the float hinge thingy.
Hmmm ... hard to be very helpful without an eyeful here.
Suggestion: Google "Suzuki (model no) adjust float level"
If you go through the replies this usually produces something which will help.
I once owned an early Honda which appeared to be factory standard, but which I became sure was over jetted.
In the end I put a piece of thin Cu wire (about half the jet hole size) through each carburettor main jet, and secured each with a bend around & through the jet inlet holes (hope you can follow that).
I ran the bike for years like that, and it was a different machine - absolutely better in every way. It did appear to be a design fault with that model.
(The bike involved here was a 4 stroke & had twin carburetors. It started cold with no choke, had difficulty revving, and hogged fuel before I reduced the jet sizing. Plug fouling was also an issue.)
Maybe something here will help. :)
imdying
30th October 2012, 09:55
I once owned an early Honda which appeared to be factory standard, but which I became sure was over jetted.
In the end I put a piece of thin Cu wire (about half the jet hole size) through each carburettor main jet, and secured each with a bend around & through the jet inlet holes (hope you can follow that).
I ran the bike for years like that, and it was a different machine - absolutely better in every way. It did appear to be a design fault with that model.
(The bike involved here was a 4 stroke & had twin carburetors. It started cold with no choke, had difficulty revving, and hogged fuel before I reduced the jet sizing. Plug fouling was also an issue.)Well fuck me dead... I thought I was the only one crazy enough to have tried that... worked in my application too :yes:
sootie
30th October 2012, 16:25
Well fuck me dead... I thought I was the only one crazy enough to have tried that... worked in my application too :yes:
Good to know my way too! The bike was a Honda CB360 twin (which I was never that impressed with).
Other point of interest is that if the wire diameter is half that of the jet hole, then remaining jet area still working is 75% of the original (not 50%).
(Remember your old formulas for the area of a circle!) :) :)
Actually I currently own a 2009 Piaggio Fly scooter which also seems to run a bit rich. I am considering a re-run of the old script!
imdying
30th October 2012, 17:58
Ooooh, I have to dredge pretty hard in the old memory banks... but I think it was related to the pilot circuit on an Holley 600 vac/sec. Was suggested to me by an older, hideously experienced joker I worked with.
sootie
30th October 2012, 19:51
Ooooh, I have to dredge pretty hard in the old memory banks... but I think it was related to the pilot circuit on an Holley 600 vac/sec. Was suggested to me by an older, hideously experienced joker I worked with.
I have an electrical background, and have usually had access to a wide range of enamelled copper wire gauges & micrometers. I usually start by finding a wire diameter which just fits the orginal jet hole & hence work out the actual jet hole diameter. From there you can measure & calculate different jetting hole sizes & try them without spending a cent! You could buy some new jets, but I have just usually left a final wire size in the hole & it has worked for as long as I have wanted. It is a good idea to document the details in a motorcycle's hand book before they are forgotten!
I have mentioned the idea to a few people, but they usually look at me as if I must be slightly demented at using such a Heath Robinson idea! Being the sort of guy I am, I get a bit of that.
Anyway, it would be an easy thing for Stoo to try, when he runs out of obvious possibilities.
Tarded
18th April 2013, 17:04
Many people are reluctant to use a solution that doesnt come in a flash box with stickers for the fairings.
Question 1 re the wire in the jets idea - does it work reliably?
There is no question 2.
Home jobs used to be how we did things in NZ - what happened?
sootie
19th April 2013, 09:58
Many people are reluctant to use a solution that doesnt come in a flash box with stickers for the fairings.
Question 1 re the wire in the jets idea - does it work reliably?
Years ago I rode a Honda 360 with the main jet in each carb modified like this, and even inspected my handiwork a couple of times over some 10s of thousands of kms.
The idea worked perfectly, and never gave the slightest trouble. Obviously, the new exposed hole size needs to be correct for carburation to be correct. I on-sold the bike with the wires in place & advised the new owner about it.
Each length of wire was about 30mm long, and it was held in place by a second insertion through one of the several main jet feed holes, and a couple of loose turns around the recessed channel into which these were drilled. I can not of course say that all main jets will be suitable for this form of wire retention.
Funnily enough, I now own a simple commuter scooter which I feel is running a bit rich. I may try this trick again! :) :)
Tarded
19th April 2013, 20:03
For the time and cost of trying you would be mad not to.
Not to mention the satisfaction of repairing stuff yourself.
Even after years as a mechanic ( and a few years since I did it for a living) I still get a kick out of home job solutions working.
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