Right I am at wit's end the fan motor stopped working few weeks back causing the bike to overheat but got back to the van.ok

replaced the fan motor with one of these http://www.modelshopleeds.co.uk/catalog/product_info.php?cPath=38_144_297&products_id=5207 MFA motor 457RE540-1 4.5-15V

Now this where its all starts going wrong next time went out the bike was cutting out /back firing only when warm even with the fan running

so I have

changed the plug

stripped the carb quite a few times now clened the hell out of it

checked for air leaks

take the stator cover off check for oil or lose flywheel

check for lose wires cleaned all the contact

once bikes warm and cuts out put new plug on ht lead and check for spark

its was almost as if the bike was running lean so droped the needed still dose it

rectifier is getting quite hot once the fan kick's in so is the drawing to much power causing a week spark once it all get to hot ?

or can you think of anything else to check ?

Is the fan spinning the right way?

Put the old fan back in. Do not over heat it. Sometimes you can push start a bad fan. Try it just to see how it runs. Or you could just buy the right one.

Edited September 24, 201411 yr by lineaway

How fast is your fan spinning? On newer bikes you can hear the fan and feel a strong air flow. I've had problems with my Ducati rectifier where it doesn't put out enough power to make the fan spin fast enough. Those model boat motors work well as replacements.

The old fan motor is shot . its spinning quite well and sucking air back through the rad but the bike when hot is backfiring and cutting out which makes me think the new motor drawing to much power causing a weaker spark ? The rectifier is getting quite hot as well

Think I found the fault I am getting 20v dc @ the fan motor side could this cause the bike to cut out when hot and is this just the rectifier or stator if the rectifier where the best place to get a new one ?

You don't say what your bike is but whatever I am 99% sure the ignition and fan circuits are completely separate.

Cutting out when hot / warm and backfiring can be a sign of HT coil failure

20V is too much for your fan, sounds as if your voltage regulator is faulty

Its a txt 280 2000 non pro i checked all the wire's time to start swapping parts out now to find out what it is

http://www.trialspartsusa.com/diagrams/Kok97to00.jpg

Perhaps the above link (wiring diagram) will help

http://www.trialspartsusa.com/diagrams/Kok97to00.jpg

Perhaps the above link (wiring diagram) will help

Been using this one think the colour seem more like my loom http://www.trialspartsusa.com/diagrams/Kok2001.jpg

I was just going by the year you gave for you bike. Both diagrams show the Transval 415 voltage regulator towards the bottom right hand side of the diagram. This is probably the component at fault, Although it says 12V expect the output may be less than 12V at low revs and up to 14.5 or even 15 as the revs rise, but I think 20 is too high.

If you live near a car garage with electronic diagnostics equipment the should be able to check you coil in a couple of minutes without removing it from the bike. You will just have to start the bike and they will clip an inductive sensor round the HT lead. This should detect a faulty coil even if the symptoms are not showing as misfiring at the time.

thanks just a quick question the cdi and voltage regulator under the head stock which way they fit back in as took the bolt out both dropped down so fail the coil is it cdi on the left or right as you stand over the bike ?

Quote

"its was almost as if the bike was running lean so dropped the needed still dose it"

Dropping the needle will make the bike more lean.

Or did you mean, you lowered the clip on the needle?

Edited September 27, 201411 yr by thats_a_five

There are separate windings on the stator for the ignition and the fan circuit.

Please notice on the wiring diagram that the regulator which feeds the fan does not feed the ignition in any way. The ignition is fed from a different winding of the stator. It is highly unlikely that a bad voltage regulator or fan motor would cause the spark problem you mention.

One sure way to confirm that, is to disconnect the regulator wire from the stator so the regulator and fan circuit are completely out of consideration. Then, wire 12 volts from batteries directly to the fan so it will run and cool the engine. Then ride.

thanks just a quick question the cdi and voltage regulator under the head stock which way they fit back in as took the bolt out both dropped down so fail the coil is it cdi on the left or right as you stand over the bike ?

It differs how they are fit with different years.

But the cdi goes on the leftside of the bike

/im sorry its not a pro model you have.

Edited September 26, 201411 yr by crazybond700