The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: emilios on 02.01. 2010 10:54

Title: first trips?
Post by: emilios on 02.01. 2010 10:54
Hi and happy new year for everyone...
I just finished my top engine rebuilt( new hi compression pistons,valves and guides) of my 1956 A10 plunger..and im very happy for that.
I read a few topics here and i learn that i must use hi octane in Cyprus we have 95 and i will use 98..
My question is for the first rides...
How long must first rides be?? 20 miles trip is ok or too long? and in what speeds?

Title: Re: first trips?
Post by: MG on 02.01. 2010 11:15
Hello emilios!

Congratulations to your successfully rebuilt engine and good luck with it!

I will describe what I usually do for running an engine in. I'm sure other people will have a different approach, this is one of the topics that is well suited to start a LOOOOOONG discussion.

Ok, now what I do is run the engine on a larger main jet (next size) for the first 1000-2000km, to give it better internal cooling by richer mixture at full load. Then I ride it solo on plain areas without going uphill. I open the throttle not more than half way and cruise around at about 80km/h maximum. Some times it is advisable to open the throttle a bit further, maybe three quarters, and accelerate a bit, in order to prevent glazing of the cylinder walls. This is only done for a few seconds, then I slow down again to about 60 km/h and let the engine cool down. So I always try to ride the bike at different speeds, accelerating from time to time, but always keep the loads and revs down for the first 1000km. Then I slowly start to raise loads and revs during the first 3000km. Then I consider it to be run in completely and able to cope with some serious riding  ;)

HTH, Markus
Title: Re: first trips?
Post by: a10gf on 02.01. 2010 11:21
Congrats for all your good work !

Some basic run-in info here:
(from )

Title: Re: first trips?
Post by: emilios on 02.01. 2010 12:49
Thanks guys...
So i know how to ride for the first 1500miles..
But what about the distance of first trip?

Title: Re: first trips?
Post by: MG on 02.01. 2010 12:57
It is not so important how long your first trip is. 20 miles definitely is okay. The engine oil should get warm, then you are alright.
If you have any concerns about your rebuild, you shouldn't drive further than you would like to push your bike back home  ;)

My first trips usually were around 40-50 km, then I usually found several nuts and bolts that needed tightening.
Title: Re: first trips?
Post by: emilios on 02.01. 2010 13:03
Dont worry MG...this is a small country.. *smile*
Title: Re: first trips?
Post by: emilios on 04.01. 2010 12:31
Well...bad news...
i start engine and left home for the first trip...
After 3 minutes i was back home again..
Engine was not running good...
Like it didnt had spark all the time...
I change plug(i had new ones on) again i checked HT leads...everything looked fine...but problem still there..
I put plug on engine block and kickstart engine...the one plug had spark ok..but the other one was a little starnge...
like it wasnt sparking all the time..i mean all the correct times..
Can a bad pick up cause this?
Title: Re: first trips?
Post by: RichardL on 04.01. 2010 12:38

Many possible problems, but first, take known good plug, wire and pickup and try them in the other magneto hole. This will rule out (or in) those easy fixes.

Richard L.
Title: Re: first trips?
Post by: emilios on 04.01. 2010 12:47
Thanks Richard..but the problem is that i dont have another magneto... *sad2*
Title: Re: first trips?
Post by: MG on 04.01. 2010 12:53
Sorry to hear that, but such small problems are common after a rebuild. Once sorted, you will surely be alright!

Like Richard said, check HT-lead, pickup, spark plug and plug cover by exchanging. Also check kill switch and cable and the points.
I had a similar problem with the magneto on the A7. After I double- and triple-checked everything on the mag (with newly wound armature) and the HT-connections, it turned out to be a faulty slip ring (new repro part). It must have had an invisible crack where the spark jumped over and finally burnt a hole in the plastic (that made finding the fault easier) *smile*
Title: Re: first trips?
Post by: MG on 04.01. 2010 12:54
What Richard meant simply was to swap the pickups incl. the HT lead and plug. If the other side is misfiring, then you know the HT lead or pickup is faulty. If the problems occur at the same spark plug, it must be the magneto itself.
Title: Re: first trips?
Post by: emilios on 04.01. 2010 12:59
OK i will try that
Title: Re: first trips?
Post by: MG on 04.01. 2010 13:07
Oh yes, forgot to mention: If you have not done it already, change the spark gap to 0.5mm. The new plugs usually have 0.8mm, which is okay for coil igniton, but too much for a magneto.
Title: Re: first trips?
Post by: emilios on 04.01. 2010 16:01
I just try to swap pickups but i cant cause they are left one and rigth one and they cant get in hole..
But i changed leads and both seems the it must be pickup or magneto.
Title: Re: first trips?
Post by: MG on 04.01. 2010 16:11
Right. If the same side is misfiring, it must either be the pickup or the mag. If you don't have another pickup, you could try this: When it's dark outside, start the bike and check the pickup for sparks arching through to the magneto body. You can also use an empty perfume bottle to spray a light mist of water on the pickup, then you will see sparks more easily. If you see any, it is very likely a crack in the pickup somewhere.
I assume you have checked the pickup brushes?
Title: Re: first trips?
Post by: emilios on 04.01. 2010 18:01
I was holding in my hand a pickup and it feld down and the brush broke...So i cant check the pickups for spark..but i will remenber that.
As about the pickup brushes i dont know how to check?
Title: Re: first trips?
Post by: MG on 04.01. 2010 18:34
You can actually just check the brushes optically. See if it is still long enough, if the spring tension is ok and if it does not get stuck in the pickup. If you have an ohmmeter you could also check the resistance from the brush to the plug cover.
After you have broken a brush, you have at least got a good reason to get a new set of pickups now.  ;)

Title: Re: first trips?
Post by: chaterlea25 on 04.01. 2010 19:21
Hi Emilios,
Does your A10 have spark plug caps fitted?
If so make sure they are NOT SUPPRESSED ie. they are low resistance,
Use a continuity tester or battery and bulb (5w) to check from the brush in the pickup to the plug connection

Make sure the sparkplugs do not have a suppressor in them
A lot of modern plugs have an internal resistor, NGK's have the letter R in the code for this

Hope this helps
Happy New Year
John O R
Title: Re: first trips?
Post by: emilios on 04.01. 2010 20:00
My plugs are the dont have internal resistor..
The plugs caps are the same i had before and they were working ok..
I do have an ohmmeter but i really dont know to use it much..
I will put one terminal on brush and the other one inside plug cap..ok i will understand that i dont have resistance?
Title: Re: first trips?
Post by: MG on 04.01. 2010 20:04
you will get an ohm reading. caps/leads that are suppressed will show several kilo-ohms, while caps without resistor and normal copper leads plus the brush will show a few ohms. So you will see if the brush/spring is making good contact and if the lead is connected to the pickup and the plug cap properly.

BTW: I made the best experience with B9HVX plugs. The NGK no.6 appears a bit too hot for an iron head engine to me. The VX plugs imho are miracle plugs concerning idle characteristics and plug fouling behaviour, they are well worth the money.
Title: Re: first trips?
Post by: A10Boy on 21.06. 2010 14:08
I was at the Banbury Run yesterday, over 600 pre 1930 bikes being taken out on the various road courses and returning, also there is a very good autojumble.

One of the stalls there is a chap called Sparkplug Man, he's something of an expert on spark plugs, I was there looking at getting some caps and a chap asked him what plugs to use in an A7. He said iron headed beezers were best on B6hs, I told him I use B7hs and he asked me if I find that they suddenly fail without warning or reason [they do], he said that B7hs's will wet up easily, and when they do they wont work again. he recommended I try some B6hs so I did.

I put them in and went out for two hours in the sunshine, the bike never missed a beat. It started easily, ticked over from cold easily and ran great. I was doing town, fast roads and country lanes.

Anyway, the moral after this long story is that I think mine runs much better on B6hs or at least so far so good.
Title: Re: first trips?
Post by: muskrat on 21.06. 2010 20:47
G'day Andy,
                    The 6's  are a little hotter so burn excess fuel better. I haven't looked back since fitting them to both my A's.
Title: Re: first trips?
Post by: BSA_54A10 on 22.06. 2010 12:59
And it will run even better with BP6's in there.
The projecting electrode dose give a more reliable spark ,better combustion and be far less prone to fouling.

Fouled plugs can be burned clean with an oxy torch.
Heat the outer case till a yellow flame emerges from the electrode valley.
Let this flame burn off then do it again, till you no longer get the yellow flame.
Now turn up the oxy ( or down the fuel ) to a lean flame and carefully heat the center dull red, hold it there for another minute or two then let the plug cool down SLOWLY.
It should have burned off leaving a nice clean white center.
Title: Re: first trips?
Post by: A10Boy on 24.06. 2010 16:29
What puzzles me about this plug fouling is that when we were lads and rode all sorts of bikes around the fields, we had oiled and wet plugs all the time, I dont remember having to swop plugs very often unless the ceramic insulation failed as we hit a tree or went into a hedge. A wet plug dried then worked, not got wet and failed totally, Is it modern petrol causing this phenomenonemonem ?
Title: Re: first trips?
Post by: BSA_54A10 on 25.06. 2010 12:43
Modern "fuel" is basically a light fuel oil with some light aromatics in there so that you can start your engine without using a preheater.
This oil is quite conductive , very sticky and non volatile so you have to burn it off.
Plug fouling is a big problem with "unleaded fuel" which is why you are not allowed to use it in aircraft.

Idling on a cold engine will increase the chances of this happening so it is now give it a swift kick followed by a hand full and hold the revs high till the bike is at full operating temperature.
Or use two plugs. a cold one for starting followed by a hot one for running.

I keep a couple of BP 5 HS in the tool box as every now and then I end up with a tank full of "slightly heavier fuel oil masquerading as petrol" and even the BP 6 HS foul at idle.

Title: Re: first trips?
Post by: A10Boy on 25.06. 2010 21:21
Title: Re: first trips?
Post by: Pete Gray on 28.06. 2010 10:44
My A7 iron head runs fine most of the time with w nice regular tickover but every now and again after perhaps a 30 mile run the tickover goes spasmodic with a tendancy to miss a beat and stall - presumably this is likely to be plug fouling as the normal running seems unaffected ?
I am guilty of not fitting new plugs for ages so am getting a replacement pair of B6HS' this week.