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thall1

4Rt No Spark - Help!

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Hi guys, I'm new to the forum - just signed up as I need some help.

I have a 2005 4rt. Just completed a oil filter/oil change and the clutch plates were removed and inspected as we had a 'judder' on the clutch.

Also checked the tappets - inlet were very slightly over so these were adjusted. 

Put the bike back together yesterday - no spark.

 

This is what I have done so far to try to cure it:

 

-Checked spark plug on a Gas Gas  - works fine

-used a Gas Gas plug against the head on the 4rt to check for a spark - nothing!

-Removed flywheel casing just to do a visible check - all seems ok. no visible wires broken on the pick up or the stator

-I have checked every connection on the bike - cleaned with electrical spray and re-fitted.

-linked out the kill button just in case.

-using the Montesa owners manual I have checked every resistance specified - all ok although the Engine Temp sensor reading is 2.7k ohms not 2.6 as per the manual.

-I have tried to 're-set' the ECU by opening the throttle wide open and kicking the bike 3 times (found this on a discussion on this forum).

-I have also opened the throttle and kicked it once, keeping the throttle open and kick start down for 30secs (suggested by another 4rt owner)

-ran a battery to the fuel pump - runs ok. (and plug is getting wet when I'm trying to start it.)

- bike has only been worked on when on the side stand or a bike working stand so its not been led on its side so hopefully its not a stuck bank angle sensor ? not sure how to check ?

 

until I started doing the checks it was only the left and right casings and tank that were removed. I have gone through these areas with a fine tooth comb to make sure nothing is tight, pinched or lose.

I am now at a loss as where to go from here....any suggestions, other than burning it, would be gratefully received!

 

 

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Remove the tilt switch, there are three wires in the connector, join the two outer wires together (creating a loop connection), leaving middle wire free, unconnected. This will eliminate the tilt switch, which can be trouble some. See if you get a spark now?

Most people I know, run without the tilt switch and just use a lanyard kill switch. Works much better, as the tilt switch doesn't kill the engine immediately (something like 15 sec or so I think), where as a lanyard will kill engine immediately if pulled.

Edited by shedracer
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Hi thanks for the info -  just tried linking out the tilt switch - still no spark!

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Hi thanks for the info -  just tried linking out the tilt switch - still no spark!

 

Only time I had  this problem was when the throttle cable was pulled up in the rubber sleeve of the twist grip, this kept the throttle open beyond the starting limit for the TPS. This kills both the injection and the spark.

In my case the cable was pulled up when dropping the bike and would not start, had no spark but also a dry plug. Retired and took home and like you worked my way through testing by the book and all was in spec. When I found the cable problem, reseated and fired up first kick. Check that you have not pulled the cable out some how, a quick look at the throttle body will tell you if the throttle butterfly is closed.

 

Good luck

 

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Occasionally wires break inside the insulation especially where they go into the back of spade connectors etc. This can kill the electrics with no externally visible sign. You need to use a resistance meter with a piercing probe to make sure electricity is getting from the connector to the wire. Also a terminal can slip back inside a connector block, examine the pin / socket positions on the connectors you have had apart.

I am not that familiar with 4RT electrics but in general (rectifier  / regulators excepted) Honda components are pretty reliable. A broken wire is far more likely to be the fault.

I would start by finding a means to spin the engine (I use a power drill on 2Ts) and measure the outputs from the components starting with the source coil, ACG, Ignition trigger and working gradually through the system to the spark plug.

The ignition circuit falls approximately into 2 parts, the bits that produce the spark (not too difficult to test) and the electronics that control the production of the spark which usually need specific diagnostic equipment

 

Edit - written before previous post

Edited by dadof2

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hi all, many thanks for the ideas....throttle body butterfly is shut so that's ones ok! -  I have just been reading the manual again.... There is no specific test for the condenser. Manual suggests replacing it with a good one if yours is suspect. Is there a check that can be carried out before buying one? 

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Hi me again!.... just been googling 'starting problems'..... one topic pinpointed a 'starter relay' Couldn't find one on the wiring diagram marked as such but looking through the parts manual I found one listed on the wiring harness. Its located right behind the rear shock in a rubber boot. have not got it out yet as its a bit tight...looks like the rear shock will need to come out first...anyone know what exactly this item does? Apparently, the part used on 4rt is common to lots of other bike makes as well and these have been experiencing problems....... 

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Hi me again!.... just been googling 'starting problems'..... one topic pinpointed a 'starter relay' Couldn't find one on the wiring diagram marked as such but looking through the parts manual I found one listed on the wiring harness. Its located right behind the rear shock in a rubber boot. have not got it out yet as its a bit tight...looks like the rear shock will need to come out first...anyone know what exactly this item does? Apparently, the part used on 4rt is common to lots of other bike makes as well and these have been experiencing problems....... 

 

That relay is for the fan ... if you do want to get it out, I find it easier to remove the airbox.

 

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When you say "linked out the kill switch" do you mean you by-passed it with a wire link. That wouldn't be right. The kill switch shorts to ground when you stop the bike so it should normally be open circuit. So to test - just disconnect the kill switch. Make sure the kill wire to the ECU is not shorting somewhere on the frame.

Otherwise I'd be checking the coil next.

Chris.

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If it was running before you took it apart, its likely to be something simple. The fuel pump connection has caught me out before, as has the earth under the ht coil. The rear shock has rubbed through the loom before. The only component failure I've experianced has been the bank angle sensor

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Hi all, with regard to the kill switch, yes I just left the circuit open.

 

a few more tests have been carried out.....

 

I have conned the wires out on the ignition side, from connectors blocks to ECU  connections and as yet I cant find any signs of a broken wire.

 

I wired a test lamp to the 4pin socket under the tank and if I push the starter by hand I  get a light. I know it does not show I have 12v at 1800rpm but at least there is something so I would presume that rules out the stator?

 

I disconnected the LT wires on the coil and fitted the test lamp in place of the coil. If I turn the engine over by hand on the kick start I don't get the lamp to light. Should I expect to get a light? I tried the same test on a Gas Gas  and I did get the lamp to flash, but not sure if I should expect the same on a four stroke with a hand start?

 

If I should get a light and I'm not, any ideas what component I should be checking next? -  If there is an issue on the fuel side, i.e. injector failure, or such like would this prevent a spark?

 

I have re-checked the pulse generator and I'm getting 96ohms - within spec. (moving/twisting the wire as it enters the casings does not have any effect so the wire appears ok)

 

No signs of fretting cables any where...

 

any more thoughts would again be gratefully received!

 

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I always try and do the easiest and most obvious problems first if possible, I assume you've checked the plug cap is fine?

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had the coil and lead put onto another bike - it works fine.......

 

I'm new to 4rt -so who is this 'well know' specialist?

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