Rough running in the powerband, knocking/pinking ? (ETZ251)

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Rough running in the powerband, knocking/pinking ? (ETZ251)

Postby keleto » Sat Sep 10, 2016 5:20 am

Between about 4800 and 5400 revs my engine seems to be knocking/pinking, or perhaps it is exhaust crackle ? It smooths out afterwards and more throttle seems to help which seems to kind of suggest a touch of lean mixture, but I already have quite rich settings and cannot really go much richer without plug fouling.

I have retarded the ignition to 2.0mm BTDC and started using premium (high octane) fuel which had made it a LOT better, but it is still noticeable. My carb needle is in the 4th position (ie one step richer than stoichiometric) and I have used a 140 main jet instead of 130. My plug colour is just on the rich side of perfect as one would expect with this arrangement. I have a morris minor air filter which is believed to be a little easier breathing than the stock one, and an aftermarket exhaust silencer (not a racing exhaust, just a generic china replacement). My squish measurement is good (1.1mm) and I am using a B7HS plug.

Any suggestions ?
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Re: Rough running in the powerband, knocking/pinking ? (ETZ2

Postby DAVID THOMPSON » Sat Sep 10, 2016 2:39 pm

try a plug of a different brand same heat

and about a week after you get a 2 smoker running perfect expect a hole in the piston top :smt040
Dave 2002 MZ RT125+1995 Saxon Tour(500cc)
1997 MZ 660 Traveller+6/13/09 WV USA
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Re: Rough running in the powerband, knocking/pinking ? (ETZ2

Postby keleto » Mon Sep 12, 2016 9:26 am

Yeah, easy to get them to run, but hard to get them to run really well. I have changed to a slightly colder plug for the moment as one was available, when the weather is nice I will try it out. Regarding a different plug brand, what brand would you recommend ?
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Re: Rough running in the powerband, knocking/pinking ? (ETZ2

Postby DAVID THOMPSON » Mon Sep 12, 2016 10:27 am

I use Bosch a lot
in the day when i had 2 smokers i used lodge and klg but i think they are not made any more at least i can not find them

my old Yamaha ym1 305 cc use the same Bosch plug as my later R50s BMW 4 stroke and was not bad about fouling them
Dave 2002 MZ RT125+1995 Saxon Tour(500cc)
1997 MZ 660 Traveller+6/13/09 WV USA
"IN the end times the IDIOTS will be in charge
of everything"
"I like the road less traveled if it's PAVED!"
wd8cyv at yahoo dot com
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Re: Rough running in the powerband, knocking/pinking ? (ETZ2

Postby AIRMANBEAR » Fri Oct 11, 2019 9:50 pm

keleto wrote:Between about 4800 and 5400 revs my engine seems to be knocking/pinking, or perhaps it is exhaust crackle ? It smooths out afterwards and more throttle seems to help which seems to kind of suggest a touch of lean mixture, but I already have quite rich settings and cannot really go much richer without plug fouling.

I have retarded the ignition to 2.0mm BTDC and started using premium (high octane) fuel which had made it a LOT better, but it is still noticeable. My carb needle is in the 4th position (ie one step richer than stoichiometric) and I have used a 140 main jet instead of 130. My plug colour is just on the rich side of perfect as one would expect with this arrangement. I have a morris minor air filter which is believed to be a little easier breathing than the stock one, and an aftermarket exhaust silencer (not a racing exhaust, just a generic china replacement). My squish measurement is good (1.1mm) and I am using a B7HS plug.

Any suggestions ?

YOU HAVE TRIED WHAT I HAVE TRIED AS WELL. TO NO AVILA...THE GERMANS HAVE TOLD ME TO INCREASE THE CHOKE A BIT TO STOP THE PINGING (USA TERM).. BUT I DONT LIKE DOING THAT ….. I HAD SIMILAR PROBLEMS WITH MY 350 JAWA AND A U.S,A. 2 STROKE RACE MECHANIC TOLD ME TO DRILL A 1/8 HOLE IN THE PISTON JUST BELOW THE LOWER RING NEAR THE EXHAUST PORT ….. THIS COOLS THE WALL NEAR THE EXHAUST PORT WITH THE FUEL/ OIL MIX WHICH OVERHEATS AND CAUSES PINKING AND SEIZURE ..
EVER SINCE I DID IT NO MORE PROBLEMS,,,,,,,,,,,,,,,,...………… ED in N.Y.
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Re: Rough running in the powerband, knocking/pinking ? (ETZ2

Postby Puffs » Sat Oct 12, 2019 4:47 am

Following a biased and flawed moderator choice (someone posting aggressive personal attacks is rewarded, while my technical posts are removed - behind my back & without any justification!), I have withdrawn from this forum.
Last edited by Puffs on Mon Apr 03, 2023 10:09 am, edited 1 time in total.
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Re: Rough running in the powerband, knocking/pinking ? (ETZ2

Postby Puffs » Thu Oct 17, 2019 10:49 am

Following a biased and flawed moderator choice (someone posting aggressive personal attacks is rewarded, while my technical posts are removed - behind my back & without any justification!), I have withdrawn from this forum.
Last edited by Puffs on Mon Apr 03, 2023 10:09 am, edited 1 time in total.
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Re: Rough running in the powerband, knocking/pinking ? (ETZ2

Postby Blurredman » Fri Oct 18, 2019 2:35 am

I imagine on a Rotary or Reed valve induction engine, it would be okay to have the hole there.. ?
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Re: Rough running in the powerband, knocking/pinking ? (ETZ2

Postby Puffs » Fri Oct 18, 2019 4:36 am

Following a biased and flawed moderator choice (someone posting aggressive personal attacks is rewarded, while my technical posts are removed - behind my back & without any justification!), I have withdrawn from this forum.
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