Popping & Banging on the Overrun

Black Panther/Street Moto, Baghira, Enduro, Mastiff, Skorpion Traveller and Tour.

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Popping & Banging on the Overrun

Postby starfield181 » Fri Jul 15, 2016 6:29 am

Slowly getting to grips with my 2004 Baghira enduro. On first test run it was making a lot of popping and banging through the silencer on the overrun. It has done about 17k miles and has no recent service history. First thought was closed up tappets. Indeed one exhaust and all 3 inlets had no measurable clearance so they are now all adjusted.

On the road it made no difference so i have now removed the Fortune after market can ( I hesitate to call it a silencer) and fitted the standard one which came with the bike. Instant improvement in social acceptability so its staying anyway despite its weight. Popping and banging still present but less offensive to some degree. not sure if its less or simply more muted.

Before doing all this I did check the pilot adjuster screw and set it to 2.5 turns from closed as per book. Engine starts easily and ticks over reliably. Needs choke to start from cold and for the first 50-100 yds, thereafter not normally needed for rest of day.

Any suggestions as to what I should look at next with regarding to the popping noises or do they all do that!

Thanks

Peter
Baghira 2004
Traveller 1998
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Re: Popping & Banging on the Overrun

Postby den » Fri Jul 15, 2016 6:53 am

yo got to pull the carb out to check for standard jets and needle position , its probably been adjusted wrong if it had a futurama can on,,mine did the same till i uprated the jets,but i kept the aftermarket endcan on ,
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Re: Popping & Banging on the Overrun

Postby starfield181 » Fri Jul 15, 2016 9:41 am

I was afraid you were going to say that. Did have a quick look at what was involved in getting the carbs off. Looked daunting, a view that seems to be commonly repeated on this forum. Every chance i will break something and create a real problem instead of fixing it. Is there anything else i can check first.

Settled for checking the pilot screw setting for now. By the way does it weaken or richen the fuel/air mixture when you screw it out beyond 2.5 turns.I have a suspicion that its running a bit rich at the pilot stage and excess fuel it's igniting in the silencer that I can hear.
Baghira 2004
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Re: Popping & Banging on the Overrun

Postby breakwellmz » Fri Jul 15, 2016 11:04 am

My standard Mastiff came with the pilot screw 6 turns out from new.
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Re: Popping & Banging on the Overrun

Postby den » Fri Jul 15, 2016 11:43 am

breakwellmz wrote:My standard Mastiff came with the pilot screw 6 turns out from new.

yep , mines about 6 turns out also,
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Re: Popping & Banging on the Overrun

Postby edfmaniac » Fri Jul 15, 2016 3:36 pm

Lots of info around here about stock jetting. Idle circuit too lean and mains are too rich from the factory. If you aren't going to open up the carbs to check the jets, you will probably want to try the 6 turns out.
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Re: Popping & Banging on the Overrun

Postby den » Sat Jul 16, 2016 5:05 am

not to mention the pesky little filter hidden under the float valve needle. :oops:
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Re: Popping & Banging on the Overrun

Postby DAVID THOMPSON » Sat Jul 16, 2016 12:55 pm

a lot of these bikes are just setting in storage..
reason is there does not seem to be any way to get the motor to really run
correct with the oem carbs
dave

mine is setting because its a gas hog
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Re: Popping & Banging on the Overrun

Postby edfmaniac » Sat Jul 16, 2016 9:15 pm

MIne was pretty dialed in before I opened it up and modified everything. It hit 45hp at the wheel and the factory rated it for 48hp at the crank if I'm not mistaken. It did have a good aftermarket airfilter conversion and a Pro Circuit silencer, but the internals and carbs were stock other than jetting.
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Re: Popping & Banging on the Overrun

Postby starfield181 » Sun Jul 17, 2016 6:46 am

edfmaniac wrote:Lots of info around here about stock jetting. Idle circuit too lean and mains are too rich from the factory.


Does opening out to 6 turns richen or weaken the fuel/air ratio? I would assume (hope) the former given the quote above. My gut feeling is that its too weak at that point.Raising the needle might also help. That should be possible with out removing the carbs?
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Re: Popping & Banging on the Overrun

Postby starfield181 » Sun Jul 17, 2016 6:54 am

Did a day visit to the Woodbridge Inn MZ camp yesterday and met up with a few old friends. Got chatting about 660 motors and I was told by one long time (from new) Mastiff owner that all of these models tend to pop/bang as standard - something he just puts up with. He also said the Skorpions do not seem to suffer from this problem even though they appear to have the same motor and carb. Don't know what if any difference there is in the jetting between the Baggie/Mastiff and the Skorpion.
Baghira 2004
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Lots MZ 2-Srokes
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Re: Popping & Banging on the Overrun

Postby edfmaniac » Sun Jul 17, 2016 2:04 pm

starfield181 wrote:
edfmaniac wrote:Lots of info around here about stock jetting. Idle circuit too lean and mains are too rich from the factory.


Does opening out to 6 turns richen or weaken the fuel/air ratio? I would assume (hope) the former given the quote above. My gut feeling is that its too weak at that point.Raising the needle might also help. That should be possible with out removing the carbs?


Out is richer, in is leaner. It's a fuel control needle valve, not an air bleed. Raising the main needle won't effect idle circuit at all.

If it's jetted right, it won't back fire and pop. You probably need a larger pilot jet. The Skorpion suffers from the same problem.
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Re: Popping & Banging on the Overrun

Postby ralf » Thu Jul 21, 2016 1:43 pm

Skorpions do do it! My 1995 Tour has been doing it since I bought it in 2001. I had to lay the bike up in early 2015 and had loads of trouble with the carbs gumming up when I came back to it in 2016. Removing the carbs I found all the settings wrong, opening point of the CV slide. pilot screw etc. so I reset it all to handbook spec with the pilot 2.5 turns out. The bike would start and tick over but wouldn't rev up. Internet research suggested the pilot screw needed to be anywhere from 4 to 6 turns out, I've now got mine at 4.5 turns out and it still pops on overrun a bit. Next time I get the urge I will take the carbs off and try 5.5 turns out. Why is the specification for the pilot screw 2.5 turns out? Can anyone describe how to adjust the pilot with the carbs in situ? I've tried all sorts of things but there's just not enough room for my hands.
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Re: Popping & Banging on the Overrun

Postby edfmaniac » Thu Jul 21, 2016 10:02 pm

The factory spec is super lean so it would pass emissions regulations. The only proper solution is to replace the pilot jet. The carb isn't designed to run at 6 turns out even though that will do the job usually. Any good dyno tech would tell you that you need to swap jets.

I have fairly fat stubby hands and can get to the screw no problem. But you'll need to find a short screwdriver or make one and it's hard to reach in there without gloves once the engine is up to temp. Anything will work for a screwdriver since there is little resistance. A wooden dowel with clothes hanger wire for example. Just pound the wire flat on one end or grind it and glue the other end into a short piece of dowel with a mark or flat spot on it, so you can count the number of turns. One of the dyno techs I used had a tool made from an old cable with a 90 degree elbow on it.
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Re: Popping & Banging on the Overrun

Postby breakwellmz » Fri Jul 22, 2016 2:21 am

starfield181 wrote:Did a day visit to the Woodbridge Inn MZ camp yesterday and met up with a few old friends. Got chatting about 660 motors and I was told by one long time (from new) Mastiff owner that all of these models tend to pop/bang as standard - something he just puts up with. He also said the Skorpions do not seem to suffer from this problem even though they appear to have the same motor and carb. Don't know what if any difference there is in the jetting between the Baggie/Mastiff and the Skorpion.


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