Mirage TS Backfiring ..

Yogi

Yogi

Hero member
Location
Bellingen NSW Australia
I've done just under 800kms on the Mirage TS since getting it registered last week and have had a ball getting used to riding a triple again.

One annoying thing has cropped up a couple of times, including this afternoon when I went out for a run of just over a hundred kms.  The engine  went fine on the way out through the suburbs running at between 60 & 80 k's, went fine on the Freeway running it at 110-130 k's.  Engine revving fine up to about 5500-6000rpm - didn't take it any further as still getting used to riding again after a few years on the sideline. 

Called in to see my brother and then came back on the Freeway, still running fine...  Reached end of Freeway and back to the 60 k zones, and the engine started to backfire off throttle just as the light of the day faded to night and temperature dropped.  Revs rising at idle to about 1700-1800 rpm when stopped at lights..

At first I thought it might have been fuel starvation and went to reserve after a while, but still no change.  Persevered for a few more k's and then pulled over as was starting to cramp in the left leg!  Switched off fuel and walked out the cramp for about 5 minutes.  Got back on bike, turned fuel on to main (as opposed to reserve) and started the engine to find it running fine, idling down to about 1300rpm, no backfiring - I rode it home the next 10 k's with the engine performing beautifully.

The carbs were set up to run in Calgary, Alberta and here I am at sea level in Sydney - difference of about 1000m, but is that an issue that could cause this to happen?

The present carb jetting is 55 pilot jets, K1 needle middle notch, AB 265 needle jet, 122 main jets, all brand new, with the idle mixture screw at about 1 and 1/2 turns out, 70 choke jets, accelerator pumps all adjusted the same.  Carbs were cleaned ultrasonically, new airfilter box, rubbers and filter.    Plugs are NGK B8ES and new plug caps fitted.  The engine has had a full service by PLC, cams dialled in, new timing and primary chains, new Wolfgang stainless exhaust.  You can see the work that PLC did here in just over 300 photos... - https://skydrive.live.com/?cid=C2D2CC48FCAE16B0&id=C2D2CC48FCAE16B0%21756

95% of the time the engine is a beauty, but the occasional backfiring has me puzzled - any ideas why it might have 'fixed itself' after I stopped for 5 minutes? All I did was turn fuel from reserve to off, and then back on to main.  It was on main when it started backfiring... could it be a fuel vent problem?

All comments gratefully received..

Yogi

P.S. Next week I will be having the Sachse ignition fitted at the local bike shop, which also has a Dynajet dyno to set up carbs and see what's what
 
Check tighten all the inlet/exhaust mounting nuts and bolts.
Could be an air leak when it warms up.

Certainly wouldn't harm to fettle the carbs with a set of gauges just in case the altitude makes a difference.
I used to be based at sea level but now I am at 900 metres. Didn't affect carburation on mine though.
 
I am going to take a guess at sticking floats in the carts
were these replaced, maybe the black ones were binned and white ones fitted?
quite often they are "too long" accross the pivot axle and can pinch a little, enough to upset the "fuel, float bowl level drops,float drops,fuel runs in" cycle.
CLEM
 
Ah, Clem - you have struck a chord there.  When the bike arrived, Paul suggested that I check that the floats were not sticking in the carb.  I promptly forgot to do this and found that as soon as I turned on the fuel, it was coming out of the overflow pipes.  I removed all of the bowls and gently raised each float to check that they were switching off when up.

Perhaps one or more is sticking again?  I'll check and see tomorrow..

Grant, I'll check all inlet/exhaust mounting nuts and bolts, though the bike ran for a couple of hours before the symptoms emerged..  And yet they disappeared magically after I turned off fuel and rested the engine for 5 mins before turning fuel back on.

Any other ideas out there?

Yogi

 
My line of thought is that maybe a gap is appearing when the engine gets really hot, then magically goes away when it cools down.
Maybe the inlet stub to head or the carb to inlet stub?
Clem's idea is sound too though.
 
..and yours has merit as well, Grant - thanks very much for your advice. 

I'll check out both yours and Clems, plus see if anyone else has other ideas for me to check.  I'm learning and grateful for the advice received from the voices of experience here on this forum...

Just ordered a Carbtune kit to use as well.

Yogi
 
Andrew where are you doing all this riding,I have a bit of sciatica,lower back trouble but when its settled down would love to come along.BTW was it a fullon bang of a backfire or a bit of low poping,the hanging idle and small popping is a classic sign of it being lean.What DYNO,everyone happy now,shop are you using.
 
Vince,

I'm glad you mentioned lean, because that was on my mind as well.  It was low popping backfire.

Riding has been a mixture of F3, The Old Road, runs across town a couple of times to show off the bike to friends, a couple of laps of the Comenarra Raceway for old times sake and a run down to Wiseman's.  

Taking it easy to start with, keeping good distance between me and cars ahead, and no desire to go above what I feel comfortable with.  Joints are not used to working like they are having to - book me in for a yoga course, someone...

I do fancy going for a ride up to the Tweed Valley and back if I can before end of year - something about the trip up the coast that I always like.  Got some smallish Oxford saddlebags the other day and will get one of their magnetic tanks bags when the place at Brookvale has more stock in.

Have to get some work done soon, though am seeing it as my daily transport for the time being.  I was going to go club plates, but then went the whole hog as I don't think that I could play by the rules of club plates for the first year, and I don't want to end up in strife over that, or cause problems for CIMAA with the authorities by flouting the rules due to my willfulness in wanting to go for a ride whenever I can.  Cost me $800 for full rego and $800 for $20,000 comprehensive.  If I go back to club plates next year it is what? $80 for rego and $130 for the same cover.

The plan is not to lose any points - had 10 years of good luck and would like to maintain that if I can.

See you on Wednesday nightbfor the NSW meeting at Alexandria..

Dyno is at Motorcycle Weaponry down at Mona Vale.  They do a few classics down there as well as the modern bikes..

Yogi
 
That's probably the only :{DYNO:} place I haven't tried over the years but I hear there extremely competent and helpful to boot,don't know about Wednesday night.Been in bed with the bad back for 4 days.That and over the counter pills usually sorts it.Pisses me off with all this great riding weather
 
Vince - got some Endone tablets the Doc gave me for kidney stones that will sort any pain out - I just lay there for a few days watching Gunsmoke, Big Valley and Bonanza, listening to my pulse.  Didn't get rid of the kidney stones, but I couldn't give a f**k after the first day... not quite as good as Morphine and you don't get the pretty nurses, but it'll get you where you want to be if you want to step on that pain...

Let me know if you are coming and I'll bring some along if you are in big pain.

Yogi 
 
Any 1200 carbs I have opened up had 65 pilots in there from the factory.

55s came with the 1000s although I have seen some 58s and 60s kicking about.

It all depends how well the head breathes. Gas flow it and you will either need bigger pilot jets or at least wind out the mixture screws.
 
The pain is there for a reason,its not to bad.I just need to let the swelling go down.Usually takes a few days.I had a mild case 2 weeks ago,didn't know why.It came back a fair bit worse and found out why.Original I was rooting around on the Pantah Ignition key switch for a while before the first onset.The back came good and I finished the job,bending and twisting to get at it for a couple of hours trying to sort out why the Parkers stayed on all the time.The penny dropped the second time.Should have known better.Bending and twisting does it every time
 
Grant said:
Any 1200 carbs I have opened up had 65 pilots in there from the factory.

55s came with the 1000s although I have seen some 58s and 60s kicking about.

It all depends how well the head breathes. Gas flow it and you will either need bigger pilot jets or at least wind out the mixture screws.
Click to expand...

I'm sure the 1200 has 65s and the Mirage has 55s or then again maybe not.

                                                                                        Dave
 
Hi,
I found this summer that original Dellorto white floats does not operate well when using 98E5 gasoline. After three months of use the floats were expanded so that they stuck between supports and caused overflow.
 
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