View Full Version : HELP !!!! Its Electrical.

Sean Atterbury - n/a
6-Feb-06, 06:18 AM
Well off we went yesterday and flew around the rugby fields again..

I have checked the filter, the carbs the plugs (the one was a bit loose, OK way loose and that could have contributed but not likely) The mix is right but still the revs veary from 5 0000 to 6 200

We rode around a bit and then when comming in to stop, when I pulled the lanyard to kill the motor, nothing happened. She just kept on going. http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif

I have checked all the wires and all is still connected, yet now all it does is 5 000 and from time to time 6 000, this is verry frustrating.

For those who do not know, my craft has a 503 duel ignition, duel carb. 2 stroke. http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

Wonderfull motor when she runs propper.

What could it be, where should I look and what needs testing to find the problem?

Thanks guys, look forward to your replyz. http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif

richardevans - n/a
6-Feb-06, 08:20 AM
So when you hold it at max throttle for a long while, does it run at a steady engine speed, or does the speed go up and down?

Or does it reach a different engine speed on different days? Are you sure your tacho is working properly?

Check the continuity and make/break action of the lanyard switch. If it's OK then your wiring has a fundamental fault.

Faultfinding is usually a case of finding the one fact that you assumed was absolutely true, but actually wasn't...

Keep trying!


Richard E.

Sean Atterbury - n/a
6-Feb-06, 08:39 AM
On full throttle you can hear as the revs drop and raise together with the tacho.

I have checked all wires and all is still as it was lastweek, connected fine. Tacho is fine too.

We did try the lanyard, I have two, as it is duel and pulling one out seems to make a little difference, this is one at a time, pull both and it does'nt die.

Maybe if I strip everything and put it back together, Air Commander on there site say that the timming could be out and thus, but no the lanyard should stop the motor no matter what the timming is.

I did some doanuts and it also seemed to rev 6 200 constantley when I turn left and when I turn right it dropped to 5 000. That also bugged me, why would it do that, does'nt make sense, I first thaught that the carbs lost pressure because of the angle of the craft, but that can't be it.

I have'nt checked for sludge in the carb yet, maybe it could be that, but again, Y would it not die when lanyard is pulled.

Very unhappy camper right now. http://hovercraft.org.uk/images/icons/smiley_icons/icon_confused.gif

richardevans - n/a
6-Feb-06, 08:54 AM
Sounds like you have two unrelated faults.

If the lanyard switches are OK then you have a wiring fault, even if you believe they haven't changed.


Sean Atterbury - n/a
6-Feb-06, 10:07 AM
Just been home and pulled the lanyards off, and reconnected them, are looking better already, will only test tonight.

Also taken off those two CDI boxes, them will have a look at later and check all connections there, also took out all spark plugs and they two look good.

Do you think that I can rev her up to 6 000 on the trailer or should I rather do it on the ground? I am a little worried about flyign off with that much thrust. http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif

At least if it does, it will mean that everything is OK. http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif

Don83000 - n/a
6-Feb-06, 01:32 PM
Yes you can run it on the trailer to 6000rpm and if you can get 6K on the trailer you should get approx 6500 off the trailer just put a couple of bricks in front of the trailer wheels and that will hold it easily. Hold it at 6K for a couple of minutes then without releasing the throttle stop it using the lanyards then check your plug colour the insulator should be a chestnut colour if its much lighter than this you are running weak and could hole a piston and you would need to richen up the carbs by lifting the needles a notch or two. Also you only need one lanyard on that engine.

Sean Atterbury - n/a
7-Feb-06, 04:14 AM

Could not run the engine last night as is started to rain and is still raining http://hovercraft.org.uk/images/icons/smiley_icons/icon_mad.gif

I will try it as soon as I get a chance.

I tried only one lanyard and could not get it to work, Can you maybe send me a diagram of how to wire it all up, that would be great. http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

The spark plug colour, is that the white bit that turns chestnut or what?

I'll get to the needle settings later, lets fix one thing at a time.

Thanks for the advise, will try it as soon as the rain stops.

Don83000 - n/a
7-Feb-06, 05:08 AM
Yes its the white part under the electrode I will try to look out the diagram for you later today

Graham Harvey - n/a
7-Feb-06, 03:21 PM
Ummm...this may sound stupid and obvious but have you checked your electrical ground? Perhaps the reason you are getting the drop in revs on a right corner is because of a loose connection on the ground (that is exacerbated when the craft leans) and this leads to a less powerful/erratic spark...drop in revs. Also a ground fault could also explain the loss of the kill cord.

Just something to quickly check...8 out of 10 times with electrical problems its a loose wire!

Graham Harvey

Paul Fitz - n/a
7-Feb-06, 11:13 PM
Don't be too concerned about the drop in revs as the craft changes direction. For some craft this is normal and depends on the fan size, type, speed and the angle at which the blades are set. Concentrate first on getting the engine to run reliably at a constant speed with the craft stationary.

This website gives some information on Spark plug colour.


But there are other, possibly better sites, search with google for "spark plug colour".

If you are unsure about the engine it is best to run it initially with a plug colour of dark tan/light brown which should be quite safe. The colour to note is the colour around the two electrodes, the insulator is less important. If you see slight white flecks forming on either electrode and an overall light tan colour the engine is running at or near its optimum, but is probably slightly too weak for safe sustained high speed use. Heavy white flecking or light grey electrodes shows the engine to be running too weak.

If you think the mixture is too weak, do not rely on lifting the needles alone. This will change the mixture in the mid to top range but will not not correct the problem at maximum revs (assuming the throttles are fully open). You will in this event need to change the main-jets.

Iwerk - n/a
7-Feb-06, 11:53 PM
The kill switch normally shorts the coil to ground. Check your connections. Sometimes people forget to remove the insulation on the wire before crimping on a connector. The crimp pierces thru the insulation and works fine until the crimp relaxes over time and then you suddenly have a problem.

The other thing that I have seen is from a very rich fuel/air mixture that will give you run-on when you shutdown. Carbon builds up in the cylinder and it keeps the cylinder hot. I have seen extreme cases where the carbon buildup will keep the engine running.



We rode around a bit and then when comming in to stop, when I pulled the lanyard to kill the motor, nothing happened. She just kept on going.

Sean Atterbury - n/a
8-Feb-06, 04:48 AM
OK checked all wiring last night, re-did everything and checked the ground, things seem better, well they did. http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif

Started her up and let it worm up.

Started to rev her up slow and at around 4 500 everything died http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif


http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif It helps if there is petrol in the tank hey.. http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif

http://hovercraft.org.uk/images/icons/smiley_icons/icon_redface.gif felt kinda doff. http://hovercraft.org.uk/images/icons/smiley_icons/icon_redface.gif

It started raining after comming back from the garage,

Will try again today.

Thanks for the tips, I did check the spark plug chart and it looks like the second from the top, wet, dry, missing.

I did strip almost everything and put back together, will try again today with a propper run up to full for several minutes and see what we end up with.

Am also going to buy a propper measuring jug to get the mix perfect from now on, before I was just using the measurements on the bottle, that is not good enough for me. http://hovercraft.org.uk/images/icons/smiley_icons/icon_sad.gif

One more thing, where is the ground on the motor , I have the ground from the lanyard and the tacho, but the motor itseld, where is that, cant seem to find it. http://hovercraft.org.uk/images/icons/smiley_icons/icon_confused.gif

Don83000 - n/a
8-Feb-06, 05:05 AM
http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif Rotax Ducati ignition wiring diagram

The grey wire is your tachometer lead - it goes to one side of the tach the other side goes to ground.

The heavy yellow wire and the heavy yellow with black strip are you 170 watt light coil, these connect to your regulator rectifier - which then charges your battery. They can also be hooked up to SOME strobe lights - CHECK before connecting to make sure your strobe will work connect directly to the system!!!

The two remaining yellow wires are you ignition kill switch one for each magneto. Connect them together then take a lead to one side of a switch and run the other side to a ground.

Sean Atterbury - n/a
8-Feb-06, 05:22 AM


Grey is already on tacho.

What lights would you recomend,? I would like to put some one, think It would look nice, maybe nav light on each corner of the craft.

The other are each connected to a lanyard, will it not make a difference if I conect them together,? I was always scared that I blow something up if I conect two wires together.

I have two different lanyard switches, one had a plastic clip and the other is a rubber boot that fits over the whole switch.

Which is better?

Don83000 - n/a
8-Feb-06, 07:27 AM
Those wiring instructions are of the official Rotax site and thats how mine is wired, as for lights whatever you fancy orange strobe beacon is the norm or nav lights.

Sean Atterbury - n/a
8-Feb-06, 08:13 AM




Sean Atterbury - n/a
9-Feb-06, 04:30 AM
NO GO, 4 800 to 5 000.

Maybe its the fuel, I checked the filter and the fuel is almost clear, the fuel I was using when I got 6 000 was a wellow colour.

I think I was using V-Power unleaded and am now using Dynamic Unleaded, could this be the problem?

Thanks for the Lanyard tip, it works great thanks for that Don. http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif

The colour of the plugs, I ran it at full or 5 000 for five (5) minutes and well the colour stays the same, white. http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif so took em out and here is a pic attached.

I think today I will take the blades back to 40 and see how she goes then, OH the mix is perfect as I used a propper measuring dish, although I failed math I mixed 142ml of 2stroke to 7100ml petrol. thus 50-1. or 2%.


OK let the comments fly, no realy smilies today, not so happy. http://hovercraft.org.uk/images/icons/smiley_icons/icon_cry.gif

tonybroad - n/a
9-Feb-06, 08:11 AM
Hello there

a white plug in a 2 stroke is not far short of meltdown i reckon (having melted a few pistons myself), you should be looking for a tan to buiscit brown colour, chocolate brown is acceptable although getting rich

it's either too much air or not enough fuel, check for any air leaking into your carb system and thoroughly clean your jets

don't fall into the trap of changing your 2 stroke mix to alter plug colour - if you add too much 2 stroke mix you effectivley lean off your mixture as there is less fuel going in 'cos there is a bigger proportion of oil in it - i messed up some pre-mixing and mixed a batch of fuel that had alrerady been mixed - the craft lasted a lap and a half

hope you sort it soon


Sean Atterbury - n/a
9-Feb-06, 08:20 AM
OK Guess I'm stripping carbs tonight, http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif


Don83000 - n/a
9-Feb-06, 12:04 PM
When you have cleaned the carbs if its no better just try running it without the air cleaners but as Tony says you must finish up with chestnut coloured plugs or you will melt pistons you may need slightly bigger main jets.

Sean Atterbury - n/a
9-Feb-06, 12:16 PM
OK nice clean carbs, did it at work, nice to work for family hey http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

Right, The jets were clean as a wistle. They are 158 B.

Is that OK? I don't know. http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif

Will try what you recommend later this afternoon.

The white part needs to be a chestnut colour hey?.

Sean Atterbury - n/a
9-Feb-06, 01:35 PM
Right http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

Went home, put the carbs back, reved her up to 5 800 for about 10 seconds then it dropped back to 5 000.

I thing it is eccesive load: BECAUSE>> http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif

Chucked the blades back to 40 and whalla, 6 600 and if I push it into the yellow. http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

So I thing if I can get 42 or another 3 blades at 40 then we will be sorted.

I have also been steeking to friends and mechanics and they have never heard of spark plugs colour changing.


So maybe we got the wrong ones, what do you all use?

Taking my sister and her son for a quick spin. http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

Always happy to give people a ride. http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

Don83000 - n/a
9-Feb-06, 04:27 PM
You want NGK B8ES plugs and tell your friends that all plugs change colour with mixture change look in the back of any Haynes manualor go to the following link :-

http://webk.ask.com/redir?bpg=http%3a%2f%2fweb.ask.com%2fweb (http://webk.ask.com/redir?bpg=http%3a%2f%2fweb.ask.com%2fweb%3fq%3dspa rk%2bplug%2bcolor%2bchart%26o%3d0&q=spark+plug+color+chart&u=http%3a%2f%2ftm.wc.ask.com%2fr%3ft%3dan%26s%3da% 26uid%3d244a52a3144a52a31%26sid%3d145F535CCBB56ABE 3%26qid%3d87C0C76EF892CA4C904A2709A41E76A7%26io%3d 0%26sv%3dza5cb0d89%26ask%3dspark%2bplug%2bcolor%2b chart%26uip%3d44a52a31%26en%3dte%26eo%3d-100%26pt%3dVerrill%253a%2bPlug%2bColor%2bChart%26a c%3d1%26qs%3d1%26pg%3d1%26u%3dhttp%3a%2f%2fverrill .com%2fmoto%2fsellingguide%2fsparkplugs%2fplugcolo rchart.htm&s=a&bu=http%3a%2f%2fverrill.com%2fmoto%2fsellingguide% 2fsparkplugs%2fplugcolorchart.htm) %3fq%3dspark%2bplug%2bcolor%2bchart%26o%3d0&q=spark+plug +color+chart&u=http%3a%2f%2ftm.wc.ask.com%2fr%3ft%3dan%2 6s%3da%26uid%3d244a52a3144a52a31%26sid%3d145F535CC BB56ABE3%2 6qid%3d87C0C76EF892CA4C904A2709A41E76A7%26io%3d0%2 6sv%3dza5c b0d89%26ask%3dspark%2bplug%2bcolor%2bchart%26uip%3 d44a52a31% 26en%3dte%26eo%3d-100%26pt%3dVerrill%253a%2bPlug%2bColor%2bC hart%26ac%3d1%26qs%3d1%26pg%3d1%26u%3dhttp%3a%2f%2 fverrill.c om%2fmoto%2fsellingguide%2fsparkplugs%2fplugcolorc hart.htm&a mp;s=a&bu=http%3a%2f%2fverrill.com%2fmoto%2fsellingguide %2fsparkplugs%2fplugcolorchart.htm

And here is a link for all the engine info you need :=

http://www.ultralightnews.ca/rotax503/rotax2strokepdf/503mai (http://www.ultralightnews.ca/rotax503/rotax2strokepdf/503maintenancemanual.pdf) ntenancemanual.pdf

Sean Atterbury - n/a
10-Feb-06, 12:19 PM
WOW http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif thats a long link///

thanks. Have saves both.

Will try run as nuch as possible this weekend, like every weekend, will update monday on how things go.

Have a great weekend all. http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

Happy hovering