Unreliable starting

[bob.keevil]

I have an Ariel Arrow with a newly rebuilt engine (new seals and rebore). The carb has been serviced, there is a new battery, new plugs and HT leads. One day it will start on 3rd or 4th kick and the next day not go at all. I've checked the timing, points and plugs. All seem OK. The same thing happens again. Any suggestions please?

[simon.holyfield]

Have you checked the coils & changed the condensers?

[brenton.roy]

Hi Bob,
In what way has the carb been serviced?
Sometimes a small amount of water (condensation / washing) in the carby can cause erratic symptoms, as can separated oil from premix.
If you find either, You'll need to clean the tank, the float bowl and blow out all jets.

I'd also double check it's not flooding.
Check that the fuel tap shuts off 100%.
If the tap works, try turning the fuel on, do whatever you usually do pre starting (tickle / choke etc) then turn fuel off. Then kick.
If this helps, you have a needle seat / float level problem.
If it is flooding, you'd expect black exhaust smoke and black spark plugs after starting.

Just a 'one in' possibility - but is the exhaust clean /clear?

[bob.keevil]

Hi Simon,

I have suspected the condensers but have been advised by those that know more than I do about 2 stroke engines that it is unlikely to be them. Do you know how to test the condensers other than buying new ones?

Thanks,
Bob

[bob.keevil]

Hi Roy,

Thank you for your reply but I am fairly confident the problem is in the electrics somewhere as when I succeed in starting the engine it runs on one cylinder from time to time. It then runs normally again.

Cheers,
Bob

[simon.holyfield]

Bob, the classic symptom of condenser failure is arcing at the points, which shows itself as pitting. However, a condenser short circuit won't do this, but it will stop the engine. If you use your multimeter on ohms, the condenser should show 'open circuit' or a very high reading (MOhms) when disconnected.

Unfortunately this method will not show a condenser that has failed open - substitution is the only way to do that.

There are many tales from my colleagues in the Bantam club about condenser failure - even new ones, off the shelf.

Check the coils while you have your meter out - you should see a few ohms on the LT side, and a few thousand ohms on the HT side.

[bob.keevil]

Hi Simon,

Many thanks for the clear, straightforward instructions. They give me the confidence to have a go. Others that I've asked have usually mumbled at me and not made any sense!

Cheers,
Bob

[simon.holyfield]

I forgot to mention Bob. Coils often fail when hot - if you can, i.e. if you can get them warm by leaving the ignition on, it would be worth checking the LT resistance (that is between the feed terminal and the points terminal) and the HT resistance (between either of those terminals and the HT terminal) with the coil hot and cold. As I said, LT should be something like 3-6 Ohms; HT should be 10,000 x that value or so - 30 kOhms to 60 kOhms.

Also, don't worry too much about what any replacement condenser looks like - if you can get one (from Halfords, for example or some local auto parts shop) that will fit, give it a whirl. You say the fault is intermittent - have a look at the condition of your points and check the connections to them, the coils, condensers and their earths.

[keith.hodgenia]

Bob, if you look in the two stoke section of this forum you will see that others have had the odd problem coaxing their smokey steeds into life. Their problems and solutions may give you an insight into how to deal with yours. Keith.

[bob.keevil]

Hi Simon,

Many thanks for the information. I'm going to be working on it over the weekend. I'll let you know if I'm successful!

Cheers,
Bob