Tuning help needed... What am I missing?

[spreeinkc]

Fuel lines aren't crossed and it's not leaking. I manually prime the bowl every time I switch jets. I assume the needle is in correctly? I know the plastic piece that slides over the end of the cable to hold it in place is in correctly. I'll double check but I swapped carbs and it still didn't make a difference... I had a new bpr6hsa in it. Swapped it this morning with a bpr7hs and again no difference.

[patthesoundguy]

Maybe you have a leak at the oil pump plug? Just a thought if other things dont help

[spreeinkc]

That thought did cross my mind since I did use a homemade plug. I sprayed carb cleaner all over the whole engine while it was running and the idle never changed. Not sure if that's an effective way to check or not? That's how I check on car engines and it's always worked...

[Dio Dawg]

Check your reeds?

[patthesoundguy]

That thought did cross my mind since I did use a homemade plug. I sprayed carb cleaner all over the whole engine while it was running and the idle never changed. Not sure if that's an effective way to check or not? That's how I check on car engines and it's always worked...

Thats the most sensible way to check that and thats how I do it on all the stuff I work on too. I have a similar issue with my express, it just runs hot no matter what. Same deal it runs up to 400 fast and climbs. Had it take out a big bore piston. I put the stock bore on with the same carb and large jet and even went bigger. No matter what the jetting it still gets hot. I have points on the express so I'm wondering if the timing is off causing my issue. I also wonder if I have bad crank seals causing my issues. I had overheating issues with the stock carb and bore so I have to wonder. I had seen here on the board where someone had come up with a leakdown test for scooter motors with some block off plates and an air compressor hose nipple placed on one of the plates I may check that out and see if it helps diagnose my issue. Or I may just go and replace my seals and see if the problem goes away. Hope you make some more progress with your issue.

[spreeinkc]

Check your reeds?

Yeah, I pulled them and they didn't appear to be closing all the way. I pulled some out of another scooter to swap them and saw it had little metal springs (?) to help close them. Found the original package mine came in and they were still in there. Thought for sure that was my problem but just like everything else it didn't make a difference.

There are three main things I can't figure out. Why does it still hit 400 with bigger jets. Why does it only run good with jets much smaller than would be expected? And even with the smaller jets (110-115) why does it still act rich and blow through most of a tank in like 20 miles?

It seems to run good though. It's a little weak when taking off from a dead stop (or anytime you hit the gas when not in the pipe powerband)(and it gets worse the larger I go with the jets) it's like there's a 2 second delay and then the pipe kicks in and it starts pulling hard all the way till it tops out. Honestly, power wise, I like the way it runs. I know something isn't right though and I don't want to smoke my bbk. That and the gas mileage suck. Not so much the price but I premix now so I can't just stop at a gas station and fill up. Not very easily anyway. I was thinking about calculating out a oil to gas reference chart and carrying around a little thing of 2t oil and a syringe and that way when I need to get gas I could figure out how many cc's of oil to add based on how much fuel I actually added. But really much rather figure out what's wrong and fix it

[patthesoundguy]

Check your reeds?

Yeah, I pulled them and they didn't appear to be closing all the way. I pulled some out of another scooter to swap them and saw it had little metal springs (?) to help close them. Found the original package mine came in and they were still in there. Thought for sure that was my problem but just like everything else it didn't make a difference.

There are three main things I can't figure out. Why does it still hit 400 with bigger jets. Why does it only run good with jets much smaller than would be expected? And even with the smaller jets (110-115) why does it still act rich and blow through most of a tank in like 20 miles?

It seems to run good though. It's a little weak when taking off from a dead stop (or anytime you hit the gas when not in the pipe powerband)(and it gets worse the larger I go with the jets) it's like there's a 2 second delay and then the pipe kicks in and it starts pulling hard all the way till it tops out. Honestly, power wise, I like the way it runs. I know something isn't right though and I don't want to smoke my bbk. That and the gas mileage suck. Not so much the price but I premix now so I can't just stop at a gas station and fill up. Not very easily anyway. I was thinking about calculating out a oil to gas reference chart and carrying around a little thing of 2t oil and a syringe and that way when I need to get gas I could figure out how many cc's of oil to add based on how much fuel I actually added. But really much rather figure out what's wrong and fix it

Do you have an android iphone there are slick 2 stroke mix apps. I have one and it rocks. I used to have the paper chart in mypocket then had an excel doc written on my pockect PC and now the android

[Dio Dawg]

I work as a mechanic in a scooter repair shop here in Hawaii and we recommend customer to run 50 to 1 ratio for most bikes which is 2 1/2 oz oil per gallon. But I would always check your plug to see how you're running and adjust from there at any mixture ratio, 50:1 , 44:1, 35:1, etc... check the plug is the right way !!

[Wheelman-111]

Greetings:

When you say "most bikes" does that include Big Bores with high RPM and compression? What results? Any oil-related failures? I don't mind using less oil than 32:1 (3% oil) but going all the way down to 2% scares me and my shiny piston. Still, I wouldn't mind less smoke and better fuel economy with a bit leaner jet. That's cheaper x2.

[Dio Dawg]

Why does everyone think using more oil is better?? More oil runs hotter its thicker than gas if you didn't realize it. Resulting in heat seizure. Sure its possible to have a lean seizure too, that is why I would always check your spark plug.OMG. That's what tuning is all about. If you think you're running lean the go up in your jetting not oil mixture.As far as my plug reading with 50 to 1 mixture with a b8hs or b9hs plug its been a constant light brown color.

[Dio Dawg]

Also what kind oil are you running? Cheap oil from any 'ol gas station or auto part store? I use a fully synthetic Power Plus oil. Other good brand are Motul 800 or Castor 927.

[Wheelman-111]

Greetings:

Although I'd be the first to agree that I am a simple-minded man, most of us are fimiliar with the concept of non-combustible hydrocarbons (oil) displacing fuel causing a LEAN condition if excessive oil for existing jetting is introduced. Extra oil may lubricate, but doesn't Vaporize and so doesn't cool the combustion chamber as well as fuel with less oil in it. Oil-Rich = Fuel Lean. That's why it's recommended to up the jetting when running extra oil, and downsize with less oil.

Once you've settled on an oil ratio, you can jet accordingly. Old outboards (I've owned a few) that ran 25:1 and even 20:1 need stupid-big jets, smoked like a coal plant, and fouled plugs pretty frequently. That's why I'm considering DECREASING from the Forum Cognisenti Consensus of 32:1, which except for abundant smoke hasn't been a problem for me.

[spreeinkc]

Sounds like your running too fat, with an air leak. Did you do any work on the crank? Or split the case? How did the motor run before you did the work?


Also, you took out the OEM reed set right? Silly question but I've seen guys install the new cut Mani right on top of the oem reeds. Is your exhaust gasket the correct diameter? New pipe with no leaks?

Ran perfect prior to modifying but was bone stock (engine wise) as well. Bottom end is stock, case has never been split. Yeah old reeds are out, no choice as I had to replace them with the new CT manifold.

Think I'm going to pull all the plastics again and do a more thorough inspection for air leaks. Also might get some good synth 2t and bump my ratio closer to 40:1. I don't have a tach but with the stock lower and not port timing adjustments made to cylinder my rpm's probably aren't much higher than stock so I should be fine. Need to go get a cooler plug too...

[spreeinkc]

I have a friend who will be in KC Wednesday, I can ask him to take a look at it if you want. Pm me, I may be slow to respond but Ill see it when Im back in service.

If your friend is still coming to kc tomorrow I would definitely appreciate it if he had time to swing by and take a quick look! I double checked for any air leak. Oil plug is sealed, everywhere around manifold and carb is sealed, and exhaust gasket it spotless around the edges so no leaks there. I'm still stumped. Plus got this Aprilia I'm dying to get running as well.

[Dio Dawg]

Any new updates? I'm curious to know if you resolve your problem.