OIL CONSUMPTION By mctojs (Read 3,242 times)

[mctojs]

hello guyz, im mctojs from the Philippines, currently owning a KYMCO SUPER 8 125. my question is this is it normal for a modified gy6 engine have a noticeable decrease in crank oil after a hundred kilometer trip?

Note: no visible smoke on my pipe...

Thank you!

[mctojs]

okay sir....
here are my modifications on my scoot..

I installed the ff:

58.5mm CHROMEBORE
26 mm manifold
power pipe
"touring" camshaft
my mechanic did the port and polish

We even checked the piston rings after 5 months to check if its already worn, we found out that its ok, it just the tip of the rings are somehow in straight line..so after we corrected, I still have the same problem.. Just last week after doing a change oil, i had a trip for 200 kilometers. Then I checked the level of oil and I found out that around 150 mL was consumed.. :oIm using ELF 10w60 fully synthetic oil..
by the way, im using stock fan, and I found no leak on any part of my engine..

what could be the possible cause?

if i convert the cylinder head breather into a larger one, would this solve or even ease my problem?
Thanks..

[wildman]

mctojs
How did you break it in??? There's a couple of possibilities here that will cause blow-by which causes the engine to blow oil & or burn the oil...

You said in your last post that the ring gaps were in a straight line... IF the rings were installed right the first time, it's vary possible for the rings to rotate out of position from lack of back pressure... If the rings have rotated that a good sign there's not enough back pressure to seat the rings against the cylinder wall 100%... If there's enough back preasure to properly seat the rings they won't rotate...

David Sr.

[mctojs]

Thanks sir David!

well I didnt give particular on how to "break-in" my scoot after my mechanic did the modification... I also noticed when we checked it after 5 months, a considerable amount of carbon deposit was found on top of piston... I really suspected the way i did the "break-in" my scoot...i was told that chromebore does'nt need "break-in" ... so i did not give much attention to it...

Do I need to change my piston rings to have this corrrected? and what would be the right way to "break-in" my engine?
Thanks sir!

[wildman]

mctojs
Well, good question... As to the exact fix, need to trouble shoot the problem to figure out if it's a back pressure problem or not, but not knowing for sure if the rings were installed properly, makes this a tough thing to do in my opinion... If it were me, I'd probably assume the rings were not installed properly or weren't properly broke-in properly (this assumption is based on the fact that I have no way to know if the rings were installed properly, I don't know the specs of your exhaust & intake + I'm not a performance expert ether)... There's a couple of ways to go about this...

You could go w/ the possibility that it's a back pressure problem... In this case, I'd make sure the rings are installed properly then add more restriction to the exhaust flow to create more back pressure (for trouble shooting purposes I'd restrict the exhaust flow at least 30 - 50%, so the results are immediate), & re tune... The ride 50 miles or so to see what your oil usage is... If oil consumption improves, adjust exhaust flow accordingly... This trouble shooting option would be the least expensive & would ether confirm or illuminate back pressure from the equassion...

OR

You could go back to square 1 & leave exhaust alone (this option is based on the idea that problems were possibly break-in related (but more expensive)... Weather you replace just the rings, or replace the whole bore kit... If I was to go this route I'd prefer to just replace rings as long as the bore & piston were in good condition... Here's the problem w/ this plan, I haven't been able to find just 58.5mm rings, I have found 59mm rings... Because of this problem I changed my engine bores to 59mm... Or replace w/ new bore kit all together (this would be my absolute last option)... Then do a proper break-in... If your problem is break-in related, your oil consumption will come back to normal w/ this option, & will show during the first few miles of the break-in period... As for break-in & chrome bores I don't know what the procedures are, I've never messed w/ chrome bores... But in my opinion a chrome bore needs a break-in period just like any other bores...

In the beginning of my scooter experience I broke-in 2 scoots w/ the "Drive It Like You Stole It" Procedure, & w/ in a couple of hundred miles both scoots were blowing oil (10 - 20 + onces of oil / 50 miles, & around 700 miles they were knocking)... I did a proper break-in on my trike & have never had a problem w/ oil consumption, I did a proper break-in after rebuilding the top end of the 1 scoot & never had a problem w/ oil consumsion... Hope this helps... The other Dawg's might have other thoughts though...

David Sr.

[mctojs]

clarification on my previous post... I did not use the 10w60 fully synthetic oil during braek-in. I used it after I did the brake-in. we used 15w40 dino oil..
i'll use 10w40 dino oil once i've installed new set of rings...

[mctojs]

hello again sir David...

I believe that my piston rings were installed properly knowing my mechanic had a lot engine passed in his hands! ( except my assumption is wrong!)..

regarding the corrective measure, since it was almost 10 thousand km since I had installed the Chromebore, would restricting the exhaust still applicable? (I still have the stock pipe with me).

If I replace new set of rings, would you recommend the use of full pressure (stock) pipe during break-in?

I have with me new set of rings for 58.5 bore. so I dont have problem with the size of rings...

[wildman]

mctojs
Well I guess the question is, how many miles did you have on it before it started going through a lot of oil??? If it was 4,000 or 5,000 miles, then I'd say stick w/ the setup you have now, if it's running good w/ the setup you have on it now as it should be tuned for that setup... Don't forget when installing new rings the cylinder will have to be deglazed (honed)...

David Sr.

[mctojs]

Okay! thanks so much sir David.. yah, its running good with my present set up..its just i'm a bit worried of oil starvation... I'll post again here the result once I've replaced my rings...

[Alleyoop]

Checking it on a HILL, that is funny. Thats like having a shutoff valve on your tank and stopping going up a hill to take in the view and then it won't start for lack of fuel flowing to the carb.
Alleyoop

[mctojs]

im done replacing my rings, and i found out that the top ring is the cause of too much oil consumption... "wide" end gap on the top ring...I'll post picture later...

I just dont know why it has such a wide gap? Is it possible to have such gap because of running on lean mixture?

[Cruiser]

Sounds like an assembly problem. Either the end of the ring was broken when the ring was installed or the gap was filed down too much when fitting the ring into the cylinder. Both cases could cause excessive oil use and increased blow-by of exhaust gases into the crankcase. If the ring broke after the engine was assembled, then the broken piece would still be in the ring groove. A lean fuel mixture would not affect the ring gap.

[mctojs]

hello guys! i'd like to share my findings regarding my rings..
Your inputs is highly appreciated.

my bore....

DSC07570 by tojobriva, on Flickr

my old set of rings and the piston...

DSC07571 by tojobriva, on Flickr

my exhaust valve..

DSC07576 by tojobriva, on Flickr

my old top ring...

DSC07580 by tojobriva, on Flickr

new top ring...

DSC07579 by tojobriva, on Flickr

I replaced my ring last friday, and a while ago, i travelled around 200 kilometer as part of my break-in process..Guys, is this the real cause why I consumed too much oil?

[sprocket]

The gap on the old top ring is way too large...