Hi Guys
Firstly thank you for all your input,veryy much appreciated. Finally solved the problem, it turned out to be a very slightly damaged thread at the tip of the bolt which engaged when dry fitting off the scoot but on the scoot with a fractional mismatch refused to thread. New bolt solved the problem. Next question Jet stack on my px is the standard 140/BE5/96 main. Ive changed the jet to a 106 ( 112 and 110 just flooded the engine) and seem to have it running ok to my ear (but I doo wear hearing aids so not sure how good that is) Is there any procedure/guide That is fool proof or does it come with experience? Cheers Andy Last edited by andyx on Fri Jun 24, 2022 8:30 am; edited 1 time in total |
![]() Fri Jun 24, 2022 8:28 am
Ossessionato
2007 Stella 225
Joined: 02 Nov 2019
Posts: 2684 Location: Rochester, Minnesota |
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Ossessionato
![]() 2007 Stella 225
Joined: 02 Nov 2019
Posts: 2684 Location: Rochester, Minnesota |
andyx wrote: Hi Guys Firstly thank you for all your input,veryy much appreciated. Finally solved the problem, it turned out to be a very slightly damaged thread at the tip of the bolt which engaged when dry fitting off the scoot but on the scoot with a fractional mismatch refused to thread. New bolt solved the problem. Next question Jet stack on my px is the standard 140/BE5/96 main. what woul be a good start point for the Main jet( I have a set which goes to 112) for the polini with a drilled filter. Cheers Andy |
![]() Fri Jun 24, 2022 8:49 am
Ossessionato
2007 Stella 225
Joined: 02 Nov 2019
Posts: 2684 Location: Rochester, Minnesota |
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Ossessionato
![]() 2007 Stella 225
Joined: 02 Nov 2019
Posts: 2684 Location: Rochester, Minnesota |
andyx wrote: Thanks Chris as you rightly surmise 112 was way too rich. I'm at 106 now and it seems to be running wellBut not keen on a lock up, any foolproof way to be sure I've got the right jetting or is it a case of feeling my way aroound to a degree. 1) CHT - cylinder head temperature - it does work especially for longer sustained runs, not as fast as EGT. Cylinder head mass has a larger mass and slower thermal change. That has left me with a seized cylinder previously. Gauge was still climbing past 350°F as cylinder locked up. I like it better for a stable or sustained reading. 2) EGT - exhaust gas temperature - quicker reaction then CHT as it's measuring exhaust gas and only has to change thermocouple mass in exhaust. 3) Wideband AFR - air fuel ratio - quicker then my EGT - it's a love hate relationship for some. I have been jetted so lean it just showed said lean and I stopped and turned it off immediately. Cylinder head and EGT hadn't had a chance to read anything. 4) Plug chops and cutting plugs open, can be a pain the rear but do work. |
![]() Fri Jun 24, 2022 9:24 am
Ossessionato
2007 Stella 225
Joined: 02 Nov 2019
Posts: 2684 Location: Rochester, Minnesota |
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Ossessionato
![]() 2007 Stella 225
Joined: 02 Nov 2019
Posts: 2684 Location: Rochester, Minnesota |
andyx wrote: Thanks Chris, got a cht probe, which I'll fit when I replace the rear shock (next job). Just want to avoid a seize and chucking my 66 year old body down the road ![]() How did you arrive at 106? If you go up one jet size how does it run? I think you said your missing a 108? Ok I see you edited previous post, you went from a 110 to a 106. Theoretically you should be ok, temperature readings would be best, maybe try a 108 if you can get one, best you can do is run on rich side for safety. |
![]() Fri Jun 24, 2022 12:16 pm
Ossessionato
2007 Stella 225
Joined: 02 Nov 2019
Posts: 2684 Location: Rochester, Minnesota |
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Ossessionato
![]() 2007 Stella 225
Joined: 02 Nov 2019
Posts: 2684 Location: Rochester, Minnesota |
andyx wrote: I've got a 108 so I'll try that over the weekend but what will tell me if a jet is too rich? |
Fri Jun 24, 2022 12:44 pm
Hooked
Joined: 28 May 2020
Posts: 451 Location: Planet Earth |
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How on earth are you considering that jet size? That's way too high. A road 2.0 sip will be no more than 102 on your jet stack and that's with derestricted air filter too. The polini isn't as powerful top speed as a road 2.0, it's a good 5 mph slower and does not rev on like a road 2.,Without seeming to be arsey we are repeating the info you ask for when it's already been given . Anything like a 108 will rich bog like hell, your plug will be black and wet. It's a standard 125 we are talking here with a rather mediocre box pipe on a standard cylinder . 101 or 102 jet !!! You are going 12 pts over standard jet with a 108, even your polini instructions will state 4 pts over standard !
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Hi ferriswolf, thank you for your input but the 106 isnt bogging (had to google that) with the polini and the drilled filter and I'm real new to this and want to avoid seizing the motor and me sliding down the road on my arse.
I'll try the 108 and if it bogs I will have an idea where I am. Until I get the cht fitted I will err on the side of rich. Will let you know where I end up |
I agree with ferriswolf. If your only mods are a Polini box and a drilled airfilter, your main jet should end up in the 100-102 range.
When you are dialing in a main jet, you are looking for splutter (better descriptor than "bog" in this context I think) at max rpm, i.e., wide open throttle in 3rd gear. It took me a while to learn the difference between a motor that was spluttering and a motor that was revving all the way out, and it is hard to put into words. Of course there is the actual splutter. Beyond that, the best way I can describe it is splutter will feel like the motor is hitting a wall, revving out will feel more like the motor has reached the end of its tether. |
Sat Jun 25, 2022 8:27 am
Hooked
Joined: 28 May 2020
Posts: 451 Location: Planet Earth |
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Kowalski wrote: I agree with ferriswolf. If your only mods are a Polini box and a drilled airfilter, your main jet should end up in the 100-102 range. When you are dialing in a main jet, you are looking for splutter (better descriptor than "bog" in this context I think) at max rpm, i.e., wide open throttle in 3rd gear. It took me a while to learn the difference between a motor that was spluttering and a motor that was revving all the way out, and it is hard to put into words. Of course there is the actual splutter. Beyond that, the best way I can describe it is splutter will feel like the motor is hitting a wall, revving out will feel more like the motor has reached the end of its tether. |
Sun Jun 26, 2022 3:09 am
Hooked
Joined: 28 May 2020
Posts: 451 Location: Planet Earth |
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andyx wrote: Thanks guys for your advice and your patience, next step I think is to fit the cht as a back up while I learn to work out what the engine is telling me. As before I will keep you updated with my progress on this learning curve. When I had it standard other than a sip road 2.0 and a derestricted air filter it's jetting was 101 and perfect. It's as simple as replacing your main jet and sticking on your air filter. This is a five minute job. Then you whack your exhaust on, about a 45 minute job. You really don't need a temperature reader. Your scooter will do the same top speed as it did before however with the polini box it will be more eager and torquey in third and from third to forth where it will reach its maximum hp as it can't rev on . If you had a road 2.0 pipe , jet would be 101/102 depending on climate , season as it does have a better top end over standard . I've run both pipes matey preferring the road 2 . I now have a dr177 bolt on and this is where the experiments with jetting , air correctors and atomisers come into play and where a temperature meter could be useful however I have learned with help on this forum how to plug read across all running speeds and the folk on here gave me the likely base jetting info for my kit as they have either got that kit or used to. So yes learn at your own pace but accept the giveaway information to start you off with and keeps it simple and cost effective . |
ferriswolf wrote: You have px 125 2003 , I have px 125 2003, it will be an MY disc model . When I had it standard other than a sip road 2.0 and a derestricted air filter it's jetting was 101 and perfect. It's as simple as replacing your main jet and sticking on your air filter. This is a five minute job. Then you whack your exhaust on, about a 45 minute job. You really don't need a temperature reader. Your scooter will do the same top speed as it did before however with the polini box it will be more eager and torquey in third and from third to forth where it will reach its maximum hp as it can't rev on . If you had a road 2.0 pipe , jet would be 101/102 depending on climate , season as it does have a better top end over standard . I've run both pipes matey preferring the road 2 . I now have a dr177 bolt on and this is where the experiments with jetting , air correctors and atomisers come into play and where a temperature meter could be useful however I have learned with help on this forum how to plug read across all running speeds and the folk on here gave me the likely base jetting info for my kit as they have either got that kit or used to. So yes learn at your own pace but accept the giveaway information to start you off with and keeps it simple and cost effective . It seems to me from all the reading I have done on this forum that developing a 'feel' for the engine is invaluable and thats what I'm trying to to in my cackhanded way. Please dont take offense if I seem to be a little slow following your advice I am just tring to do it in a measured way that makes sense to me. Please stick with me as I know your advice/help it the future will help me when I fit a kit, which will be neccessary if I am ever to make the sidecar outfit viable. I see we live in the same county, maybe we could meet up for a chinwag( coffee's are on me) |
Sun Jun 26, 2022 6:54 am
Hooked
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Posts: 451 Location: Planet Earth |
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