Rota Arm Problems on MG Midget Race Car
Discussion
Boyfriend was racing at Silverstone this weekend and an on going problem keeps occurring with his car. A brief run down of the problem is that the rota arm keeps burning out.
Whilst racing at Silverstone, on the LAST lap, the car all of a sudden starting running lumpy, went bang a few times and stopped. When we looked at the car at the circuit, it turned over but didn’t always give a spark.
His dad went and brought a new rota arm, and the car’s started no problem. Trouble is he cant keep buying rota arms and not finishing races. It happen the time before at Brands.
Any ideas why the rota arms keep burning out?
Whilst racing at Silverstone, on the LAST lap, the car all of a sudden starting running lumpy, went bang a few times and stopped. When we looked at the car at the circuit, it turned over but didn’t always give a spark.
His dad went and brought a new rota arm, and the car’s started no problem. Trouble is he cant keep buying rota arms and not finishing races. It happen the time before at Brands.
Any ideas why the rota arms keep burning out?
The electronic ignition should not be what is causing the burn.
My first thought is that the rotor is not correctly aligned with the posts in the dizzy cap at the point when the spark fires. The result is that the spark has nowhere to go so tries to arc down into the dizzy shaft.
Has the dizzy been modified to remove advance and retard? If so then it may have been locked in a position causing the misalignment.
Same applies if it has been fitted with an electronic sensor instead of the points this could also cause the misalign.
Steve
My first thought is that the rotor is not correctly aligned with the posts in the dizzy cap at the point when the spark fires. The result is that the spark has nowhere to go so tries to arc down into the dizzy shaft.
Has the dizzy been modified to remove advance and retard? If so then it may have been locked in a position causing the misalignment.
Same applies if it has been fitted with an electronic sensor instead of the points this could also cause the misalign.
Steve
sounds much more like a cap problem causing a symptom on the rotor arm.
teh ignition system will generate a voltage depending on where the biggest gaop to jump is in the system ..
has the dizzy cap been changed recently and if so was the correct type fitted?
if the rotor arm has a flat top ie no spring loading on the contact to teh centre of he dizzy cap then the cap must have a sprung loaded plunger, if not there'll be a massive gap there and the spark will be jumping that gap, the KV will be sky high and that could be your problem
rule is:
sprung loaded cap centre elctrode = plain rotor arm
rigid cap centre electrode = sprung centre on rotor arm.
any mismatch and you'll have problems.
teh ignition system will generate a voltage depending on where the biggest gaop to jump is in the system ..
has the dizzy cap been changed recently and if so was the correct type fitted?
if the rotor arm has a flat top ie no spring loading on the contact to teh centre of he dizzy cap then the cap must have a sprung loaded plunger, if not there'll be a massive gap there and the spark will be jumping that gap, the KV will be sky high and that could be your problem
rule is:
sprung loaded cap centre elctrode = plain rotor arm
rigid cap centre electrode = sprung centre on rotor arm.
any mismatch and you'll have problems.
A bit late, I know but....
My money is also on the carbon bush in the top of the dizzy cap. I've had the same symptoms (although not managed to burn completely through a rotor arm)on my MGB. Took a couple of goes to get get a decent cap too. Quality of parts seems to be dropping.
Sheepy
My money is also on the carbon bush in the top of the dizzy cap. I've had the same symptoms (although not managed to burn completely through a rotor arm)on my MGB. Took a couple of goes to get get a decent cap too. Quality of parts seems to be dropping.
Sheepy
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff