TRX250R.ORG
Workshop => Engine and Bottom End => Topic started by: Pricecheck on February 17, 2014, 09:27:41 PM
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Here's what I have going on. It was about 45* 1,100' elevation out today and I decided to finally do some plug chops. I did the normal warm up and the whole sequence that is called for. I'm running 32:1 VP C12/Castor 927 mix, 39mm PWK, 330 +4 stroker and an 01 cr250 ignition. No advancements or retarding of timing. Also running a B8es plug gapped at .018.
My first setup today was dgh 2nd clip, 50 pilot and 185 main. It looked like the pictures below but lacked the blackish ring the whole way around the plug top (whatever that is called). It was a chocolate color but only near the strap.
The pics below are from my adjustment run of dgh 2nd clip, 50 pilot and 188 main. As you see, the top area is a uniform color the whole way around. Both runs resulted in the electrode being barely brown and the strap anneal line being near the base.
(http://forums.trx250r.org/vbulletin_imports/250_732_2017-04-18_7537.jpg)(http://forums.trx250r.org/vbulletin_imports/250_733_2017-04-18_4024.jpg)
I'm trying to understand how I can get that nice paper bag/chocolate brown shade to the electrode and that nice anneal line around the bend of the strap. B9 series plug? Increase the gap? Retard or advance timing?
Note: It does feel very slightly lazy on the top end. I know it wants to pull more but it just doesn't seem to be all the way there. It does move out but just seems ever so slightly flat up top. Maybe I'm just expecting more since I love going fast!
Please help. I know there are hundreds of threads on this stuff but I'm just trying to find a solid answer quickly.
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I have read that you can read the plug by looking at the soot around the ground base ,most people cut the treaded part off and look at how high the ring comes up the porcelain,'i believe it should be 2 mm high,as far as the tan color goes,jt will happen with time on the plug but isn't used to read it,try a 9 and see if the blueing moves to the midway point.most 250r guy believe that .018 is the way to go but I only think so if it is needed because of misfire
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I was recommended an 8 series but I might try some 9 series to see what it does. Everywhere I'm reading says that my plug is too hot. I know my idle is rich as well. I'm getting plenty of smoke, almost too much. If I ride normal my plug gets a black coating all over everything but no clumps of anything. Just rich. I'm already running a 50 pilot but I think I might double check my air/fuel mixture once I get this plug thing fixed. Overall it pulls great across the board so it might be safe to keep it rich down low to mid since I run in that range.
By the way, thank you for responding!
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you should probably start with the slow jet,move to the needle and then main.I really don't think you get a good main reading when the motors trying to clean out all the extra fuel
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Sounds like you are on the right path:
(http://honda-tech.com/attachment.php?attachmentid=275310&d=1339246218)
Be careful with a 'G' length needle, it is pretty lean in the midrange. Going with a 'D' or 'E' length (DDH, DEH) might help darken up the plug. See if you can cut the threads off to see the fuel ring at the base of the plug.
(http://www.jetsrus.com/photos/photo_keihin_needle_N427_48_aftermarket_chart.JPG)
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I am see a large number of customers burning pistons as a result of following published misinformation about reading spark plugs. There are some beliefs that are wrong and becoming very popular on the internet. A spark plug is NOT an device that can read air fuel ratio. An O2 sensor will not accurately read air fuel ratios from a high performance two stroke engine. I would like to dispel some of the misunderstanding that laymen have about reading spark plugs. I do not want to offend those that have taken considerable time to publish/pass on this information unless the members here want me to pass on some of my experiences with tuning engines and reading spark plugs.
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I am see a large number of customers burning pistons as a result of following published misinformation about reading spark plugs. There are some beliefs that are wrong and becoming very popular on the internet. A spark plug is NOT an device that can read air fuel ratio. An O2 sensor will not accurately read air fuel ratios from a high performance two stroke engine. I would like to dispel some of the misunderstanding that laymen have about reading spark plugs. I do not want to offend those that have taken considerable time to publish/pass on this information unless the members here want me to pass on some of my experiences with tuning engines and reading spark plugs.
By all means Jerry.. please post your insight.
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I'd like to hear Jerry's expert opinion and technical advice on plug reading for sure..
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always good to hear the experience of others, please share Jerry
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The way I read plugs for gas is to read the insulator ring like shown in the picture, but the strap reading has not been very consistent IMO on gasoline
For alcohol I look at the flat surface of the plug exposed to the combustion chamber and look for about half of this surface to have the zinc plating to be discolored
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Jerry, please share
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I would also like to hear Mr. Hall's thoughts on the Gordon Jennings 2-stroke articles/book.
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Jerry, please inform us.
As of now I picked up eight B8ES plugs to try out. I might just have to pick up a new needle. If not for use, at least to try out and/or have options. I've actually heard that the dgh needle could never be fine tuned easily with my engine. Maybe this was for people who wanted peak hp in every bit of the throttle. Do I want this? Hell yes I do! I would just rather be running just a little rich to be safe. Tomorrow I'll be working the chops again to see what they yield.
Jerry, to give an update here's what I'll have tomorrow to work with: 330 stroker, 39PWK (50 pilot, 188 main, 1 1/4 turns air/fuel, 3 1/2 slide screw, dgh 2nd clip), TRX5 pipe and silencer, k&n with outerwears in lidless stock box, 32:1 VP C12/Castor 927, 01 CR250 ignition no advance/retard, and riding in Kansas weather at 1,100' altitude and about 45*-50* weather. Misc crap that affect cooling and drag.... pwk radiator, 14/36 gears, o-ring chain, 20" rears. I know it isn't needed but it's what is going on.
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I would also like to be informed! I'm very curious about this stuff.
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Here's a quick two WOT runs with the 9-series plug. No jetting or needle changes.... (http://forums.trx250r.org/vbulletin_imports/250_775_2017-04-18_3262.jpg)
You can ever so slightly see the line on the strap. Down at the base of the ceramic I could see what looked to be a couple millimeters of darkness. You can see that the ring is covered at about 3/4 of it. The top of the electrode will still not get any darker.
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Looks good, cut off the threaded area for a better look at the ring at the ceramic base
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Here is with a .022 gap (no difference felt or seen) and the dgh back to the 3rd clip with two WOT runs. The darker line is blurry (due to camera) at the bottom of the strap.
(http://forums.trx250r.org/vbulletin_imports/250_776_2017-04-18_8132.jpg)(http://forums.trx250r.org/vbulletin_imports/250_777_2017-04-18_6050.jpg)
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Looks good! I would leave it where you are at
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Dave, thanks for the advice. I just tried a cej on the 3rd clip but it had a little more sputter up top and it seemed to burn off the ring a little more (leaving it more of a dark gray haze) but slightly darkened the top area of the ceramic some. I didn't like the strap color though. Was just a shot to see if I could get just a little more pep out of the low end.
Now when I run it normal at a conservative pace and shifting I get more of a complete black ceramic. If I put that plug back in and do some WOT throttle runs it seems to clear that up. Is my low/mid running rich or is that normal? I ask these questions but I'm pretty sure I'd just rather run rich, especially if it's running fine. I do think tomorrow I'll throw in a 190 main just to see if it likes it. I'll also be putting that dgh back in there.
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Below is how I look at the numbers of the needles to make a educated guess of what kind of change to expect
By changing from a DGH to a CEL you can expect 3 changes because you have changed 3 diminsions of the needle
The first letter is the "Needle Taper" which influences largely in the 1/2+ throttle position
The second letter is the "Needle Length" which influences largely in the 1/4 throttle position
The third letter is the "Needle Diameter" which largely effects the 1/8 throttle position, The pilot and airscrew adjustment also effect this area
So your change is the following when you removed the DGH and installed a CEJ
D is richer than C for the taper - so you leaned the bike at 1/2+ throttle
G is leaner than E for the length - so you richened the bike at 1/4 throttle
H is richer than J for the diameter - so you leaned the bike at 1/8 throttle
Now all these circuits (taper,length and diameter) over lap each other so at certain throttle positions it may act very much the same as the other needle but then start to lean or richen at a higher or lower throttle position
(http://i870.photobucket.com/albums/ab265/rsss396/250r%20site/keihin_single_jets_needles__throttle_valves_jet_needles_for_pe_pj__pwk_zps32930002.jpg)
(http://i870.photobucket.com/albums/ab265/rsss396/250r%20site/NeedleEffect_zps5da598e3.jpg)
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Dave, thanks for the advice. I just tried a cej on the 3rd clip but it had a little more sputter up top and it seemed to burn off the ring a little more (leaving it more of a dark gray haze) but slightly darkened the top area of the ceramic some. I didn't like the strap color though. Was just a shot to see if I could get just a little more pep out of the low end.
Now when I run it normal at a conservative pace and shifting I get more of a complete black ceramic. If I put that plug back in and do some WOT throttle runs it seems to clear that up. Is my low/mid running rich or is that normal? I ask these questions but I'm pretty sure I'd just rather run rich, especially if it's running fine. I do think tomorrow I'll throw in a 190 main just to see if it likes it. I'll also be putting that dgh back in there.
I think reading plugs at part throttle is the hardest thing because until you use some sort of throttle stop its very hard to recreate the same throttle position time and time again, I really try to use the seat of the pants feel for how the bike runs for the lower throttle positions but use the WOT plug readings like you just did in you earlier pictures
IMO just a little rich but not fat pulls better at lower rpms and a little lean on top makes the best power, but to lean will make less power so you have to be carefull.
Maybe try leaving the CEJ in and increase the main jet size to a 190 and adjust your air screw for off idle-1/8 throttle adjustment
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Alright. I'll look into that. Unfortunately the day I have time was just now taken up by saddle shopping since we're buying an Arabian horse and have to drive an hour one way.
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Did some runs. Cej with 190 just sputtered at all but low. Went back to dgh and 190. Did well. I like it. In the future I think I'll try and get a needle like the dgh but have the low if the cej. Maybe a dej?
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So did the DGH with 190 main seam better than DGH with the 188? You are using kehien main jets correct? never ever use aftermarket main jets they can be way different in flow.
what you have to determine is this a lean breakup or a rich breakup. Seams like a lean breakup so if 190 seams to be a step in the right direction then adding some fuel with the clip position may help without buying a new needle. You want to move the clip lower so it raises the needle and effectively shortens it and richening the 1/4 throttle
Try messing with the air screw and pilot if you want try adding or taking away some fuel around the 1/8 or less throttle position
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I would also like to hear Mr. Hall's thoughts on the Gordon Jennings 2-stroke articles/book.
I bought the first edition of the Two Stroke Tuners Hand Books Gordon Jennings published. It was turquoise in color and about 1973. I was in my 1st year of Engineering studies and my foundation in physics and high-level math was weak at this point. Gordon did a good job of making me think about some of the ways I had been doing things and I did not need high-level math to do any of his recommended calculations.
Jennings seemed to have a lot of experience working on two strokes but I do not think that Jennings's was educated as an engineer. It appeared that he had the aptitude to become a top-notch engineer if he had taken the time to study all of the stuff that is taught in the colleges of engineering at most major universities.
I believe that engineers are born and not created in a university. I have seen many guys without the aptitudes for engineering get engineering degrees that are terrible engineers. I have seen many guys that have an aptitude for engineering that never went to college do things that astonish their piers. Getting a formal engineering education at a university will give you about a 20 to 30 year head start over someone that is an engineer by "experience".
My mentor is a genius and is 91 years old, he never went to college (his family could not afford to help him) and can he can usually get me back on track with just about any project I need help with. He has a string of patents a mile long on all types of things. One of his patents is still used on the navigation system used on just about every commercial airliner flying. He has worked on projects for a host of aircraft companies as well as many top secret military projects that after 40 years he still cannot talk about.
As my engineering education progressed I was better able to understand what was published in the SAE papers that engineers from many of the engine manufactures and Professor Gordon Blair for the Queens University of Belfast had published. Studying the SAE papers gave me a whole new level of understanding of two strokes. While doing my engineering studies, I started a shop in my parent’s garage. I had a mill, lathe, dyno, cone rollers, porting tools, tig welder, mig welder, and a torch to weld pipes.
I started modifying engines and doing a lot of dyno testing while in college. I found that that the formulas for ports and pipe that were in Jennings's book, did not work very well on the types of two stroke engines I was working on. The guidance I received from the SAE papers was more accurate and produced much better results.
I think that Gordon Jennings's book is a very good introduction to the world of two stroke engines. Just be careful in placing very much faith in his formulas. Two-stroke technology has come a long way since the engines that Jennings used as state of the art models in his book. Be careful with some of his conclusions and theories on reading spark plugs.
I am trying to get my thought organized on how to present my experience on reading spark plugs. Looking at spark plugs is not an exact science like most of the authors of articles I have read want you to believe. A lot of tuners I have been associated with make errors reading spark plugs because they do not consider the variables that influence what they are seeing when they read a spark plug. I may need to write a book to provide the readers with enough foundation so that they can better under stand what the spark plug can reveal and why and what the spark plug cannot reveal to someone studying it.
Not knowing the level of understanding that the majority of the readers on this forum has about engines and basic physics, it would probably better for me to make a statement and brief explanation and let guys ask questions so that I can try to give an explanation that most will understand.
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I just did another run. It wasn't fair since it was about 14* colder than earlier (54* down to 40*). I ran the dgh on the 4th clip to richen it. Once running normal for awhile and finally getting the engine truly warmed up like always I performed a plug chop. This resulted in a little more brown color on the top area of the ceramic and just a tad even dark 2mm ring at the base. One thing it did do was not cover the ring on top of the plug as much. There was actually a bare area.
It did give that pull down low like the cej did. Maybe tomorrow will be like it was today in temp and I can get a good comparison from the clip on the 3rd to the 4th.