Glitches! Possibly ignition interference

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Steve McDonald
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Glitches! Possibly ignition interference

Postby Steve McDonald » May 14th, 2018, 7:24 pm

Went to test fly an aircraft yesterday but was getting radio glitches when engine was running. For CoG purposes I have the two Rx batteries, the ignition battery and the ignition unit just behind F1, along with at least a couple of pounds of lead. Could this be the cause or does anyone have any other ideas? I would like to keep the batteries where that are or I will need even more lead but I will be led by the experts! BTW it's a Thor 45cc engine with the stock ignition.

Any advice most welcome, as always.

Steve

arthur barlow
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Re: Glitches! Possibly ignition interference

Postby arthur barlow » May 14th, 2018, 8:31 pm

check you've got the right spark plug with a r in it

Steve McDonald
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Re: Glitches! Possibly ignition interference

Postby Steve McDonald » May 14th, 2018, 9:08 pm

Will check that out Arthur.

Thanks!

Tony Collins 1073
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Re: Glitches! Possibly ignition interference

Postby Tony Collins 1073 » May 14th, 2018, 9:45 pm

Steve.
Correct spark plug is BPMR6F plug.

Its internal resistance should be checked - 5000 ohms or could be a bit more.
Meter reading between spark electrode and metal plug top.


The screened lead should have good continuity with the plug cap.

The receiver batteries and ignition batteries should be kept well apart.

The ignition unit if room should be in the engine housing.
battery too if possible.

The ignition switch should be as far forward as possible

Receiver as far rearward as possible.

Always let a freshly charged receiver battery settle for a while to enable

the very high full charge peak to normalise.

Tony

Bob Thompson1894
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Re: Glitches! Possibly ignition interference

Postby Bob Thompson1894 » May 15th, 2018, 8:56 am

I have had this with a faulty plug lead. Also make sure the aerial(s) on the Rx are clear of the engine and not blanked by it.

Steve McDonald
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Re: Glitches! Possibly ignition interference

Postby Steve McDonald » May 15th, 2018, 5:39 pm

Tony Collins 1073 wrote:Steve.
Correct spark plug is BPMR6F plug.

Its internal resistance should be checked - 5000 ohms or could be a bit more.
Meter reading between spark electrode and metal plug top.


The screened lead should have good continuity with the plug cap.

The receiver batteries and ignition batteries should be kept well apart.

The ignition unit if room should be in the engine housing.
battery too if possible.

The ignition switch should be as far forward as possible

Receiver as far rearward as possible.

Always let a freshly charged receiver battery settle for a while to enable

the very high full charge peak to normalise.

Tony


Tony,

Many thanks for the pointers, I will attempt to address all of them but some will be easier than others due to the short nose on the aircraft. I might need to extend the nose or alternatively, source a lead propellor. :lol:

Steve
Last edited by Steve McDonald on May 15th, 2018, 5:42 pm, edited 1 time in total.

Steve McDonald
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Re: Glitches! Possibly ignition interference

Postby Steve McDonald » May 15th, 2018, 5:41 pm

Bob Thompson1894 wrote:I have had this with a faulty plug lead. Also make sure the aerial(s) on the Rx are clear of the engine and not blanked by it.


Bob,

Thanks for the reply, I'll check the plug lead but the Rx should be OK as it is well out of the way.

Steve

Steve McDonald
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Re: Glitches! Possibly ignition interference

Postby Steve McDonald » May 15th, 2018, 6:03 pm

[quote="Steve McDonald"][quote="Tony Collins 1073"]Steve.
Correct spark plug is BPMR6F plug.

I have just checked the spark plug and it is a BPMR7A which differs from the one quoted above. Will this make a difference? Haven't measured the resistance as yet.

I wish I had kept the old plug but was sure I cross referenced it to the BPMR7A, unless of course it was the wrong plug to start with!

Steve

arthur barlow
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Re: Glitches! Possibly ignition interference

Postby arthur barlow » May 15th, 2018, 6:32 pm

it is still a resistance plug thinking outside of the box could you mount the ignition unit on the engine side of the firewall

Steve Perry
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Re: Glitches! Possibly ignition interference

Postby Steve Perry » May 15th, 2018, 6:35 pm

From the NGK site, the R6F is 5,000 ohms and the R7A 10,000

Steve McDonald
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Re: Glitches! Possibly ignition interference

Postby Steve McDonald » May 15th, 2018, 6:38 pm

arthur barlow wrote:it is still a resistance plug thinking outside of the box could you mount the ignition unit on the engine side of the firewall


Not as it is at the moment but I could extend the nose by fitting a box that I could mount the ignition on. I might allow me to shed some of the lead I'm using to balance it!

Steve

Steve McDonald
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Re: Glitches! Possibly ignition interference

Postby Steve McDonald » May 15th, 2018, 6:47 pm

Steve Perry wrote:From the NGK site, the R6F is 5,000 ohms and the R7A 10,000


Thanks Steve

Quite a difference! With the resistance being higher, I assume that less current will be drawn by the spark plug giving a weaker spark. Although it runs, would you advocate changing it for the R6F?

Steve


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