polini pimpin, 5kmi corsa overhaul

[burnt_toast]

decarbon'ed my corsa bore, piston and pg long, flushed case, custom 50cc head (polini head was stripped) with new custom base & head gaskets

this is after 5,000 solid semi-daily riden miles. night and day difference

before and afters:

[carp]

Intresteing,Good photos,can you give wheelman some tips?.....hahaha..... Lot of build up in those exhaust areas.A little strong on the oil?If I remeber,you use top quality 2 sroke oil?Any thoughts?Not much in other areas.Thanks,Carp

[Dac]

daaaaaaaaamn

what did you use to clean it all up????

[maddog]

use synthetic oil and you will not have that problem.

[burnt_toast]

Intresteing,Good photos,can you give wheelman some tips?.....hahaha..... Lot of build up in those exhaust areas.A little strong on the oil?If I remeber,you use top quality 2 sroke oil?Any thoughts?Not much in other areas.Thanks,Carp

Yup, was premixing castor927 at 32:1 ratio and wouldn't have it any other way When first built after breakin did 40:1 mix for a while but it wasnt enough for continous WOT runs and had a small seize

My jetting was always quite rich and I believe thats what cause most of the carbon buildup over time.

Also castor927 is known to keep the combustion chamber clean and send all deposits towards exhaust. I'll definitely agree with that after pulling the polini head, barely any carbon on it but certainly lots towards the exhaust.

daaaaaaaaamn

what did you use to clean it all up????

lotsa elbow grease

my friends fire pit to decarbon the pipe, looks awesome now and smells like bbq! haha

electric dremel with wire brush for the piston

and same demel with sanding drums for the exhaust port, this took about 5-6 heavy passes! that one mound in the pic is just after ONE pass

[mousewheels]

Considering the service manual says to decarbon every 2k miles, yours at 5k looks clean to me

BTW - Did you check/change out the rings? I'm impressed at the 5k life of your Corsa... Was going to ride my Elite stock awhile, but 5k life, would last years for me so might as well get to it!

[Arnadanoob]

Based on what I saw in the first few pics, your jetting is considerably rich and if I were to take a guess, it's your main jet that's too big, but then again you ride for miles at wide open so I guess that's expected.

The hard carbon on the piston and the exhaust ports are from using an inferior grade of oil, I know you used Castrol 2t which is not good to use on a high perf bore like a Corsa. Castor 927 is IMO one of the best oils to use but it doesn't have the same quantity detergents like other synthetic oils because castor oils work radically differently from other synthetic oils because castor oil doesn't need detergents to help disperse because castor (when heated beyond the flash point) starts to polymerize. All synthetic oils need detergents to help disperse the post combustion byproducts otherwise they'd leave behind large amounts of carbon buildup. For detergents you'd have to look at a normal synthetic like Motul, Amsoil, etc (anything with a JASO FC or FD rating) in hopes of cleaning up some of the excessive carbon. Amsoil's Saber Professional used at 50:1 to 32:1 works really well as it's one of the few FD-rated oils out there. BTW never use oils at less than 50:1, ever.

However the most you should see as far as buildup from using Castor 927 is some carbon at the exhaust gasket and some soft carbon on the top of the piston that should wipe clean with some solvent and a rag. If you use a very good oil there should be zero carbon buildup in the exhaust port. Your next teardown will look radically different if you start with Castor and stick with it, it will look very new. The carbon buildup at the exhaust nipple can be dealt with periodically by scraping it out with a pick, however unplugging the carbon buildup in the baffles will require either a heat treating, chemical wash or simply to cut open, repack and reweld the pipe together. The 1 bad thing about using Castor oils in a moped is that it will plug up the exhaust faster.

Otherwise it looks pretty good.

[burnt_toast]

Based on what I saw in the first few pics, your jetting is considerably rich and if I were to take a guess, it's your main jet that's too big, but then again you ride for miles at wide open so I guess that's expected.

The hard carbon on the piston and the exhaust ports are from using an inferior grade of oil, I know you used Castrol 2t which is not good to use on a high perf bore like a Corsa. Castor 927 is IMO one of the best oils to use but it doesn't have the same quantity detergents like other synthetic oils because castor oils work radically differently from other synthetic oils because castor oil doesn't need detergents to help disperse because castor (when heated beyond the flash point) starts to polymerize. All synthetic oils need detergents to help disperse the post combustion byproducts otherwise they'd leave behind large amounts of carbon buildup. For detergents you'd have to look at a normal synthetic like Motul, Amsoil, etc (anything with a JASO FC or FD rating) in hopes of cleaning up some of the excessive carbon. Amsoil's Saber Professional used at 50:1 to 32:1 works really well as it's one of the few FD-rated oils out there. BTW never use oils at less than 50:1, ever.

However the most you should see as far as buildup from using Castor 927 is some carbon at the exhaust gasket and some soft carbon on the top of the piston that should wipe clean with some solvent and a rag. If you use a very good oil there should be zero carbon buildup in the exhaust port. Your next teardown will look radically different if you start with Castor and stick with it, it will look very new. The carbon buildup at the exhaust nipple can be dealt with periodically by scraping it out with a pick, however unplugging the carbon buildup in the baffles will require either a heat treating, chemical wash or simply to cut open, repack and reweld the pipe together. The 1 bad thing about using Castor oils in a moped is that it will plug up the exhaust faster.

Otherwise it looks pretty good.

Not true man, I've used the Castrol 2t on the Corsa for BREAKIN ONLY. I run the castrol 2t oil solely for my injected setups, not for premixers.

For 90% of Corsa's life so far I've used Caster927, the other 9% I briefly tried Amsoil and Motul, but stuck with the Caster.

Yes jetting has purposely been over rich, for 35 mile+ daily commutes at high speeds, quite happy at the results happy to clean carbon than blow my cyl

I am quite certain that my carbon build up is due to the rich settings I've used, this time around I am going to retune a bit leaner and still stick to the Castor927.

[Arnadanoob]

I stand corrected, my apologies. I've never seen an engine look like that from using Castor 927, there's a lot more carbon than in any of the engines we've built for our customers. In contrast, the exhaust port on an engine using castor looks brand new with a honey-colored glaze on it (from castor polymerization) and no carbon. I'm very sure that Castrol 2t has a very weak detergent additive package unlike Motul and Amsoil so the byproducts of its combustion tends to be a lot more dirty which is why i never use it on any of my own or customer's bikes for any reason. I'm very particular about the oils I use and recommend for others.

I don't know why some folks are convinced that they need to use an inferior grade oil for proper break in. A lot of Hawaii guys think the same way but for that much physical wear to occur in such that 100-200 miles of initial riding is going to cause enough metal to metal contact to wear in the parts correctly, using that oil would cause enough wear in weed whackers, lawn mowers and other 2 stroke engines to the point of (ring) failure in just a few thousand miles of use. See, in order for parts to wear out from friction (the theory of using a lower grade oil), metal to metal contact must occur at some point because as long as the moving metal parts are suspended by a layer of lubrciant, there can be no wear. For proper break in, for folks believing this theory will also suggest using more oil, which would suggest higher internal temperatures (from being a tad lean) but will have a lot of lubrication, which is counterproductive towards the goal of wearing the internal parts from friction. Being extra lean in this stage is very bad since the piston is the first thing that'll start experiencing higher than normal temps, which leads to the piston expanding too much, which leads to possibly seizing new bores.

The main reason why parts conform to each other is from heat cycling. You can properly heat cycle a brand new bore kit using castor oil from the start or use any quality synthetic oil as long as you jet properly for that oil type and oil ratio. The most important factor during the break in is temperature and time between heat cycles. The more you heat cycle, the faster the break in. Ride a mile, stop the engine and let the engine cool. Ride a few more miles, stop and let the engine cool. Rinse and repeat. Vary the throttle often during this period.

[burnt_toast]

all good points arnadaman! noob is just not a fitting * for you

and hey mousewheels, I didn't change the rings. they looked okay and compression was good before teardown.

I've heard others claim of corsa's lasting 10-15k miles before needings rings, so decided to wing it and stick with what i got

[Arnadanoob]

The way you jet Toast (rich), combined with using Castor 927, I think your rings are going to outlast the life of your house.

Just kidding, but you're right, the rings on a Corsa (chrome top ring) lasts a VERY long time.