matt.c
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 posted on 28/12/09 at 06:11 PM |
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ROTAX KART PROBLEM BEC OWNERS MIGHT KNOW
I posted this on a kart forum but the locosters might be able to help too?
"Many thanks to everyone who helped with my last threads about my rotax starting problems. As instructed by yourselves i used a new plug and
charged battery (just a top up again)cleaned filter and carb and added new fuel and vrooom!!! It ran like a dream!
So i thought i would take it down to my local airfield  for an hour to give a good run. Ran it really steady for 15mins to let it warm up but as it
was very cold it didnt get that warm. Up and down the run way without a splutter then suddenly cough cough and stopped. Thought at first i had run
out of fuel but not i still had half a tank. Pressed the starter and now the starter wont engage the fly wheel. It spins but doesnt engage. Tested
battery for power and is was at 11.25v.
Now before i start pulling apart what i dont know much about i thought i would ask you guys for help. First question is how to fix the starter problem
and second question is what might have happened to the engine to make it stop like that?
Have checked connections but cant test for spark untill i can sort the starter problem.
Could you give me a list of things so i can check them all.
Many thanks for your help guys. It's much appreciated."
A question to all BEC owners: What volts should a bike battery be at full charge?
I have one of those batterys on my rotax max kart and it died today and just need to know if it could be the battery?
Matt
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franky
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| posted on 28/12/09 at 06:14 PM |
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you can put gaffer tape over the rad to get the heat up, you'll have to be careful not to cold seize it.
bike batt should read the same as a car really, however my old rotax cart had a smaller battery than a bike on on it?
I had starting problems once and it was down to the sprag clutch, have you checked all teeth on the starter wheel are ok?
also if it was a cough cough then cut out it could be the jetting, rotax's are very sensitive to jetting. if it was jetted for a warm day and
you ran it in a day like today you might have holed the piston. have you pulled the plug out and had a look?
[Edited on 28/12/09 by franky]
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matt.c
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| posted on 28/12/09 at 06:20 PM |
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OH crap!! What would i be looking for if i took the plug out?
I didnt run it anywhere near max revs and wasnt abusing it. 
[Edited on 28/12/09 by matt.c]
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franky
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| posted on 28/12/09 at 06:28 PM |
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pull the plug out and shine a torch down, you'd see if the piston was holed. if you pull the plug out you'll be able to see if it was
running lean too by checking it.
Rotax's are great toys but do need looking after.
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flak monkey
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| posted on 28/12/09 at 06:29 PM |
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Theres only 2 things that could be wrong to stop it running. Its 2 stroke right?
Fuel or spark.
It could just be a case of there being some muck in the fuel system and its clogged the carb.
As franky says, cold weather will require bigger jets to keep the mixture right as well.
If its spark, I know nothing of the ignition system on a rotax. Is it electronic ignition? If so then it could have just packed up as the battery has
gone flat. Could also be the reason for the starter not engaging properly.
If the batts at 11.25v with no load, its definately flat. As soon as it sees a load it will probably drop to about 10.5v. The batt should be at about
12.5v fully charged with no load.
David
Sera
http://www.motosera.com
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carpmart
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| posted on 28/12/09 at 06:33 PM |
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A 12v lead acid battery, be it a car or bike battery, should show around 12.75 volts at full charge.
You only live once - make the most of it!
Radical Clubsport, Kwaker motor
'94 MX5 MK1, 1.8
F10 M5 - 600bhp Daily Hack 
Range Rover Sport - Wife's Car
Mercedes A class - Son's Car
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matt.c
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| posted on 28/12/09 at 06:35 PM |
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quote:
Originally posted by flak monkey
Theres only 2 things that could be wrong to stop it running. Its 2 stroke right?
Fuel or spark.
It could just be a case of there being some muck in the fuel system and its clogged the carb.
As franky says, cold weather will require bigger jets to keep the mixture right as well.
If its spark, I know nothing of the ignition system on a rotax. Is it electronic ignition? If so then it could have just packed up as the battery has
gone flat. Could also be the reason for the starter not engaging properly.
If the batts at 11.25v with no load, its definately flat. As soon as it sees a load it will probably drop to about 10.5v. The batt should be at about
12.5v fully charged with no load.
David
The rotax uses a total loss system, meaning it doesn't charge the battery so it could just be the battery. Dont want to make the mistake of
buying a new one and it not working.
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franky
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| posted on 28/12/09 at 06:36 PM |
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11v will be fine..... my current bike is a 1200cc v-twin and it'll start on anything over 10.5, dropping to 8.something when cranking so will a
little stroker you should be fine.
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flak monkey
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| posted on 28/12/09 at 06:38 PM |
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Hook it up to a car battery and see if it will go
By what franky says, sounds like its probably ok anyway.
Sera
http://www.motosera.com
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matt.c
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| posted on 28/12/09 at 07:02 PM |
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quote:
Originally posted by flak monkey
Hook it up to a car battery and see if it will go
By what franky says, sounds like its probably ok anyway.
Im a bit worried if i would fry the electrics if i done that? What you think?
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flak monkey
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| posted on 28/12/09 at 07:03 PM |
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Should make no difference. A 12v batt is a 12v batt. The only difference is the Ah capacity which determines how long it will last.
David
Sera
http://www.motosera.com
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phoenix70
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| posted on 28/12/09 at 07:06 PM |
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what kind of oil are you using to mix your fuel, what ratio? Was it freshly mixed fuel?
Also the rotax was notorious for going through batteries, have you got a new battery for it?
Cheers
Scott
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matt.c
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| posted on 28/12/09 at 07:12 PM |
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quote:
Originally posted by phoenix70
what kind of oil are you using to mix your fuel, what ratio? Was it freshly mixed fuel?
Also the rotax was notorious for going through batteries, have you got a new battery for it?
Cheers
Scott
50:1 ratio and good oil.
Not got a new battery yet but looks like i will just have to buy one and try it.
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matt.c
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| posted on 28/12/09 at 07:34 PM |
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quote:
Originally posted by flak monkey
Should make no difference. A 12v batt is a 12v batt. The only difference is the Ah capacity which determines how long it will last.
David
Just tried it and my other car battery is nearlly flat too!! 
I checked the voltage of the battery when i press the start button bear in mind its not turning the engine over as the starter is not engaging and
just spinning and its 9.4v which seams to be a little low to me. What you think?
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Dangle_kt
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| posted on 28/12/09 at 07:47 PM |
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I was going to ask if you had put oil in the fuel, as I know a few people who have had fun for about 10-15 mins until the old fuel/oil mix gets weaker
and weaker as they have just added unleaded not knowing about the oil!
1 lunched engine.
Fingers crossed it is cheap to fix!
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boggle
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| posted on 28/12/09 at 08:35 PM |
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also check the power valve is not stuck...when i raced a max we would constantly change jet sizes to suit the air temp too.....
they are a great kart, what chassis is it on?
also check the oil in the starter gear box.....
just because you are a character, doesnt mean you have character....
for all your bespoke parts, ali welding, waterjet, laser, folding, turning, milling, composite work, spraying, anodising and cad drawing....
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antonio
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| posted on 28/12/09 at 08:35 PM |
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rotax do need a good batt. to work properly because it runs without alternator.
your batt may be good enought to start, but not to run engine at revs (hope that make sense)
buy a decent batt (avoid the cheap alternative and buy a rotax one).i was used to replacing them about once a year.
cheers
by the way, 50:1 ratio is 5 per cent of oil,isn't it? i've been runing all my engine @ 3 per cent max.too much oil will destroy your
exhaust valve very quickly.(wich need to be cleaned after each use)
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GaryM
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| posted on 28/12/09 at 09:25 PM |
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The starter motor and bendix assembly are easily removed and any damage should be very apparent. The gear on the end of the starter is the most
fragile so i'd start by removing the starter.
From memory, even very flat batteries usually managed to engage the bendix but couldn't turn the engine over fast enough for it to fire.
Any chance the carb might have iced up?
I've got a workshop manual i could email you but it's over 4Mb.
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matt.c
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| posted on 28/12/09 at 10:53 PM |
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UPDATE WITH PIC
GOOD NEWS!!
Have found a broken wire in the charger wire. Need to convert it to croc clips.
My charger is on of those trickle chargers for bikes.
Can anyone tell me which is the positive part of this connecter? Is it the inner or the outer? How can i test to find out?
 
Description
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boggle
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| posted on 28/12/09 at 10:59 PM |
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test meter...put the posotive in the middle and negative on the outside, you should read plus volts, or negative if you are the wrong way round....
nice toni...i had a wright chassis on my max.....
just because you are a character, doesnt mean you have character....
for all your bespoke parts, ali welding, waterjet, laser, folding, turning, milling, composite work, spraying, anodising and cad drawing....
u2u me for details
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PLEASE NOTE: This user is a trader who has not signed up for the LocostBuilders registration scheme. If this post is advertising a commercial product or service, please report it by clicking here.
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matt.c
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| posted on 28/12/09 at 11:07 PM |
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quote:
Originally posted by boggle
test meter...put the posotive in the middle and negative on the outside, you should read plus volts, or negative if you are the wrong way round....
nice toni...i had a wright chassis on my max.....
Thanks. I drove it for the first time today before it broke down!! And i thought my BEC indy was quick!!! 
It nearlly ripped my head off when the power valve cut in! Managed to loose it in a straight line!!
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boggle
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| posted on 28/12/09 at 11:20 PM |
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i was running a 96 tooth rear sprocket as it seemed to suit the track i raced endurance on...i also had the sring in the power valve changed so it
came in earlyer, made a difference on the twistyer circuits.....
not fun when you flip one thou...
good luck and enjoy
just because you are a character, doesnt mean you have character....
for all your bespoke parts, ali welding, waterjet, laser, folding, turning, milling, composite work, spraying, anodising and cad drawing....
u2u me for details
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Nash
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| posted on 29/12/09 at 01:23 AM |
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Matt,
A quick note about he starter motor on the MAX.
GaryM referred to it in his post (Gary and I go way back and have raced both together (Le Mans 03) and against each other (just about everywhere
else). What he referred to is that the starter is fragile. The copper connector to one of the computator bushes has a tendancy to snap. The symptom is
nothing happens when you press the starter button.
You can check the brush connector by finding the rubber cover on the starter motor (this is the cover to the brush connector). Give it a waggle while
pressing the starter and the kart will fire if its the connector. MAKE SURE YOU KEEP YOURS HANDS FREE OF ANY MOVING PARTS ESPECIALLY THE CHAIN
DRIVE!!.
Changing the connector is straight forward but can be fiddley as the springs used to push the brush onto the computator have a mission to interfere
with the seating of the end cap.
Starter Motor is on the DVD I mentioned in the U2U.
...................Neil
It's What You Do Next That Counts.
Build It, Buy It, Drive It:
Southern Kit Car Club
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