New G15 poor running

Information relating to the Matchless G15 or AJS Model 33 750cc twin. This also includes the G15 Mk II and the G15/45
Member
Posts: 153
Joined: Fri Jan 01, 1999 12:00 am
Location: HAMPSHIRE UK

New G15 poor running

Postby ranger » Mon Apr 25, 2005 3:11 pm

Hi Stuart

Unfortunately I am not experienced with any form of electronic ignition, I presume you meant ignition not injection. However, a couple of things to check:

Is the fuel relatively new? Modern fuels do go off quite quickly.

Are the plugs good and of the correct grade?

Is it timed correctly? Most Atlas engines have now been rebuilt using flat top Commando pistons instead of the original dished atlas items. This requires timing change from 32 deg to 28 deg BTDC.

Are carb jets blocked? Again I have heard that modern fuels can gum up the jets quite quickly.

The smoking could be caused by wet sumping or an inlet valve with no stem oil seal or a worn one. There are differing views on whether wet sumping is acceptable or bad for the engine. But I've always found that the pump soons scavenges the excess oil and doesn't blow any seals providing it's left idling for around 5 mins. To check for wet sumping: Run engine for 10 mins then stop and put engine onto compression, then drain oil from crankcase plug for 2 hrs. Note that it is normal for the crankcase to hold around a pint, and the timing case between 1/2 and 1 pint. Rremove drip tray from under crankcase then using a clean tray, see how much oil drains through engine over a period of 24 hrs. If more than approx 150cc, the pump would benefit from lapping in which is an easy straightforward job which I can explain later. Use of straight 50, or 40 oil also helps prevent wet sumping.

My starting procedure on all my P11s is: Use no choke (haven't got them fitted). Flood carbs, open throttle half way for 30 secs. Turn on ignition, ease kickstart onto compression, open throttle very slightly, give mighty kick and they usually start second or third kick, unless people watching then it can be embarassing but not as bad as many Gold star owners I've watched.

Anyway, good luck.

Tim Roberts

Member
Posts: 153
Joined: Fri Jan 01, 1999 12:00 am
Location: HAMPSHIRE UK

New G15 poor running

Postby ranger » Tue Apr 26, 2005 8:44 am

Stuart

I have always been happy with the standard points set up on my coil ign bikes and standard, but very good condition, magnetos on others. I know of so many people who have had probs with electronic ign, either thru poor quality of manufacture, or their own poor wiring using bad crimps/connectors fitted with 99p crimping tools. Anyway, lets not get into any debate, just my preference.

Wet sumping - If the contents of your oil tank are in your engine, then it will be difficult to spin over fast enough on the kickstart. Also, there is the possibilty I suppose of blown seals, as it's a lot of oil for the pump to scavenge quickly, that's if it spins fast enough to start!

Many people I know have fitted on/off taps or one way valves in the oil line but, personally, I don't really like either. I know that I would one day forget to turn on the tap, and there is a failure rate associated with all auto valves which, however small, would result in a catastrophic event. From being in the aviation game for over 30 yrs, I know that we try to design out single point failures, compensate with dual facilities, or introduce scheduled replacement as a lsat resort. Anyway, enough waffle, what you really need to do is take the timing cover off and check a few things.

Is the crankshaft end seal (in timing cover) OK), if torn, this can be the problem. Is the small conical oil pump seal on side of pump OK? Both of these should be replaced anyway as small cost whilst timing cover is off.

Is the pump body face perfectly flat and mating with the crankcase face properly? To check, take the pump off (2 nuts) and check both the pump face and crankcase face for flatness. Also check the pump end plates do not portrude beyond the machined pump face and hold the 2 machined faces apart. Check the pump end float - there should be none, if you have some and the pump is very easy to rotate, it needs replacing or lapping. Replacement costs around 200 I think, lapping costs around 3-4 hours of your time. Alternatively, people like Norvil can overhaul your pump for around 80 I think. If you want to know the lapping procedure instead of buying a new pump, reply here and I'll document it.

Cheers

Tim

Member
Posts: 2438
Joined: Mon Jan 01, 2001 12:00 am
Location: NORTHAMPTONSHIRE UK

New G15 poor running

Postby lawrence » Wed Apr 27, 2005 8:03 pm

Hi Stuart
Personally I think the Boyer is a quantum leap over mag or coil/points and I have bikes with both. The only weak link is the loom. All connectors must be excellent and definitely soldered, crimping will cause problems. If you suspect the Boyer it can be tested by running a wire direct from the battery. Boyer have an excellent free helpline and they will tell you of all the tests. once it is right, which is easy to achieve, it is FANTASTIC [:)]

Lawrence [}:)]

Member
User avatar
Posts: 617
Joined: Mon Jan 01, 2001 12:00 am
Location: KENT UK

New G15 poor running

Postby Tolly » Thu Apr 28, 2005 8:09 pm

I agree with Lawrence, I converted my G5 and it certainly makes a big difference. I was advised, by Boyer, that it is a better practice to use 12 volt so I converted this also but I think that is the easiest bit. [8D]

Regards, Mike T

_______________________________________________________

Experience is something you don't get until just after you need it.

Member
Posts: 153
Joined: Fri Jan 01, 1999 12:00 am
Location: HAMPSHIRE UK

New G15 poor running

Postby ranger » Fri Apr 29, 2005 9:02 am

Crimping does not ever cause problems if you invest in aircraft quality crimps and a similar quality crimping tool at around 30. Soldering is a pain in the butt to me, particularly difficult in some tight areas and possible to melt the covering if not careful. Soldering was invented before crimping was fully refined and understood, however, I can understand the reluctance to spend 30 on a quality tool. Luckily I have been able to borrow them for 30 years but will be buying one now that I'm changing career.

Tim

Member
Posts: 2438
Joined: Mon Jan 01, 2001 12:00 am
Location: NORTHAMPTONSHIRE UK

New G15 poor running

Postby lawrence » Fri Apr 29, 2005 7:29 pm

Hi Tim
you are right that there is a world of difference between high quality crimps and the usual diy type and of course all vehicle electricians use crimped. Boyer still recommend soldered joints though but of course you have to have the correct (Jap) connectors. Vehicle wiring Products, so very helpful and efficient on 0115 9305454 have everything you could ever need on electrics and give superlative advice.

Lawrence [}:)]

Return to G15 / AJS Model 33

Who is online

Users browsing this forum: No registered users and 2 guests