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Discussion Starter #1
Folks,
As the title describes I have been having an irregular misfire in both cylinders and if I blip the throttle quick from idle it will cut out, sometimes it will catch up and rev, other times it will stall the engine. If I rev it relatively slowly it revs up fine, but still has a slight mis-fire. If I take it for a spin, it cuts out on a load (going up a hill) at low RPMs similar to when I blip the throttle in neutral. Here's the rundown on the machine:

New to me last fall and it was barely running when I bought it- due to dirty carb passages and having sat for a while. I took the carb (stock amal 930) apart, replaced the needle, needle jet, main jet (all to original specs), return spring, aluminum/viton float needle, gaskets, thick o-ring to manifold, manifold to head- gaskets, and inspected float height. The slide (3 cutaway) has a little wear on the bottom-front.

I have adjusted valve clearances, strobe timed it (Lucas Rita EI), installed new plug wires(had the original lucas!), new plugs (have tried both ngk br7es and champion n4c) and spark looks good. Can you detect misfire spark just by looking at it while kicking it over? It looked regular to me.

I checked fuel flow (about 320ml/min), gas cap is venting fine, no air leaks in carb to manifold to head. Compression is good. Battery is new and fully charged- and tests well under a load.

What do you guys think? Electrical or Fuel? Would some bad wiring or grounding cause the symptoms I described? Maybe the old amplifier?

The fuel in the tank is from last fall- but I treated it with ethanol stabilizer. I'll drain the tank tomorrow and put some fresh stuff in.

Any thoughts you guys have would be greatly appreciated!
 

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Most of what you have sounds good.I think you'll find 3-1/2 slide cutaway is recommended.The 3 slide would make it a little rich around 1/4 throttle.You can file the cutaway at a steeper angle,to get 7/32" of cutaway.

I'd suspect electrical problems,especially a voltage drop in the ignition wiring.The most frequent cause of voltage drop would be the kill switch.
You could try running a wire from the battery directly to the ignition box (include a fuse and a switch in the wire).If that doesn't help,you may need to look further in the ignition.
 

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Discussion Starter #4
Mr. Pete, One other question on timing:
I have read conflicting advice on proper RPM for strobing Lucas RITA EIs. Should I be aligning the pointer and timing mark at 3500 or 6500 RPM. Some things I've read stated the manual is a mis-print and it should actually be timed at 6500. So not wanting to rev it that high I timed it at 3500 leaving it a degree or so retarded to allow for additional advance. Should I time it to allow full advance (pointer and mark on rotor) at 3500?
 

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Discussion Starter #5
Thanks Mr. Pete- you got me on the right track. I wired in a switch/fuse to the ignition box and boom- fired on first kick, lights brighter, turn signals faster, horn louder, and throttle response is better and no cut-out under a load. When I was rigging the wiring I noticed the fuse holder which was there before was pretty banged up so I hooked my new fuse holder/wire (sans switch of course) back to the regular circuit through the kill switch etc. and boom again- fired first kick and ran as good as with the bypass.

It still has a slight miss- I'll wait back to hear what you have to say on the timing RPM before I dig into it further. I might go through all the wiring connectors to make certain everything is clean and tight.
 

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If its original equipment Lucas Rita,it will have full advance at 5000.It's only 2 degrees less than that at 3500.
If the timing mark is accurate and it lines up at 5000,you should be OK.

Aftermarket Lucas Rita systems will reach full advance at 6500 rpm.

If it's a carburettor problem it will only happen at a certain throttle opening.Have you still got the rich slide cutaway?

Ignition problems usually get worse at high engine load,and more worse at high rpm.
 

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For what it's worth - my 1978 (with points) was misfiring. It turned out to be a bad contact in the bullet connector that ran from the points to the coils. The bullet connector was under the tank. Once I cleaned it up and squidged it a bit, no more misfiring. I wasted a couple of hours messing with the carbs trying to solve this one.
 

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Discussion Starter #9 (Edited)
Thanks for the input guys. It's a slight misfire at idle and through the throttle range so I would venture that it might be electrical. Back to the timing- how do you know whether the Lucas Rita came from a bike which had it as original equipment vs aftermarket? Different amp? Or reluctor? Mine has the AB5 amp (finned box).

Thanks cybersausage and Dave- I'll check those connectors and get a fiberglass pen!

-Joe
 

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I took my RITA out about a year ago after it went iffy.

I don't think mine had fins? I can look tonight. It was the original, or as good as since I bought my bike in 84, so it's within 5 years of new

Alan Osbourne of AO services can fix sick RITAs but I went with more modern tech, Vermont's a fair distance from the uk to be posting the kit
http://www.aoservices.co.uk/index.htm
 

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For what it's worth - my 1978 (with points) was misfiring. It turned out to be a bad contact in the bullet connector that ran from the points to the coils. The bullet connector was under the tank. Once I cleaned it up and squidged it a bit, no more misfiring. I wasted a couple of hours messing with the carbs trying to solve this one.
I had exactly the same problem with mine, and it was the connector under the tank, I have since run a separate cable from the timing chest direct to the EI missing out the existing loom altogether.
 

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Discussion Starter #12
Dave- it's just a skip and a jump across the pond right! I actually just got a morgo pump from the UK, the world is small these days. But yeah I'd probably give up on the ol' Lucas if it came down to it. Don't worry, I won't get anyone started on "the best EI's".

Strobed it and set it right on at 5000. I checked out the bullet connectors from the reluctor and they looked spotless, but cleaned them anyway and reconnected. While pawing through the wiring around the coils and battery I did find a ground wire half-arsed taped up and when I peeled the tape back there was a pretty bad cut. I also noticed some wire insulation cracked around the base of the female connectors which attach to the coils. I'll get some new connectors and fix the bad ground wire- but next winter will be the time for a new loom. The miss is so slight, but bugs me anyway. Thanks for the tips and I'll keep you guys updated!
 

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I know what you mean - I fitted a short front mudguard from a T140D but couldn't find the innner brace anywhere in the UK. I got one from the states with 7 day turn around.

cough.....Pazon. 7 year guarantee and polarity protected for idiot proof installation
 

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Discussion Starter #14
cough.....Pazon. 7 year guarantee and polarity protected for idiot proof installation
I was leaning towards Pazon, I have only read good things about their EI's. What were the symptoms of your lucas rita failing? Is there any way to detect a misfire issue in the amplifier using a multimeter on Volts or testing resistance? Or will that only work if the amp is completely defunct?

I went through all my connections and cleaned/replaced as needed, but still has the slight misfire.
 

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I used the tests listed in the workshop manual ( classic bike biz if you don't have one) and spoke to Alan Osbourne.

My bike just cut out at odd times and refused to pick up under load. To be honest, maybe I could have fixed it, but I lost faith and fitted the Pazon over an evening with an afternoon to time.

I cranked the bike to exactly the timing mark before taking the RITA off, so was 99% there when refitting the new one.
 

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Discussion Starter #16
Thanks for the help guys, she's running good now and the miss is gone! I did a bunch of things, so I'm not sure what solved it. I torqued the head and rocker boxes, adjusted the valve clearances, rev'd the bike for 30 sec without the exhaust to seat the valves, adjusted the pick-up clearance, and fixed a connector from the alternator. I'm not sure which did the trick, but it's running good now.

I'll try to get through the season with the current EI, but will throw a Pazon and new wire loom on next off-season. I'm looking to install a PODtronics in the near future as my local triumph guy has one ready to be thrown on. Thanks again guys.
 
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