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Post by drewzard6688 on Apr 6, 2022 12:12:52 GMT -5
After I got the cvt where I liked it I ended up getting a 70cc kit, the iron stage 6 streetrace. I've been working on getting the jetting right in the stock carb but our weather has been prohibitive right now. the yasuni r and streetrace want to pull over 10k rpm so its a little bit worrisome knowing I have to use my own judgement to keep it in the safe rpm range. If I did it again I probably wouldn't get the polini variator stuff. I did also end up putting a chinese vino clone seat on, one with the passenger pad on the back. It fits alright and only needs minor trimming. The oem seat is way nicer, and the foam on the clone actually has less room on its main portion, I have to wiggle back to the longer section to actually sit comfy. The lower straight across bars I have also make it less roomy. I plan on recontouring the foam for a taller rider.
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Post by Zino on Apr 6, 2022 19:43:29 GMT -5
Drew The Street Race and Yasuni is quite a racy combo .
That should really twist the speedometer past 40 mph and make racing from street light to street light so much more fun .
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Post by drewzard6688 on Apr 6, 2022 21:57:44 GMT -5
Zino its a good bit faster than before. Still dialing it in.
I had the bike shut off on me while riding, was breaking it in and it just cut off. Wasn't much above 300*f and only 1/4 mile from my house but it just shut off and I coasted to the shoulder. Temp might have been creeping up on part throttle, I was trying to keep to the break in procedure. At WOT the 72.5 jet was the first size small enough to actually ride. Was a very spooky incident. Started right up and went home. Was running a smaller jet than I expected, only one size bigger than the same pipe on 49cc, 70->72.5. All of my bigger jets ( 75,77.5,80+) just bog bog bog and it won't rev high enough to even shift. Could my carb bowl have emptied faster than fuel could fill it? I don't know. Tore the 70cc kit off and its still brand new looking. Plug was a milk chocolate brown but not overly oily.
Sooner or later I will break down and order a wideband 02.
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Post by Zino on Apr 7, 2022 8:00:45 GMT -5
Sounds like a soft seize
I use the genuine mikuni main jets stock carb with stock airbox . 70-75 is a range that works for me .
Part Throttle and on deceleration is where a lot of soft seizes happen . If you were cruising at 1/2 throttle and you are above 300 degrees that is running pretty hot . I only am at 300 plus when I am above 3/4 throttle . Around town driving 1/2 throttle or less I am in the mid 200's.
Richen the needle up by lowering the clip a notch or 2 . Taken the richest setting that has best throttle response.
Your Plug Color tells us your overall tune is rich enough but it can still be lean on the pilot or needle .
I have run the stock carb with racier setups like yours It works ok but you cannot dial it in as tight for performance and safe temps at all throttle positions
A Carb upgrade to a 17.5 or 19 mm dellorto makes a big difference in safe temps and performance .
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Post by drewzard6688 on Apr 7, 2022 10:45:27 GMT -5
The needle was already one notch rich, will try dropping it to the richest setting. A new carb is probably on the horizon. Crank would be nice too. Weather is a bit cold out for any long riding today but warm enough to test.
What's the best way to test and tune a main jet on a scoot that will rev higher and ride faster than you want?
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Post by Zino on Apr 7, 2022 18:35:18 GMT -5
Pick a good road that you rip it wide open . The stock crank can handle being above 10k rpms you just dont want to hang out there all the time . If you are worried about rpms you always can up gear it the will drop your peak rpms 5-10%
Carb tuning I start way to rich and run high speed runs going up 20% and working down I want it to be so rich that it gurgles . I run he richest main jet that gives me the best top speed .
Then I work on the needle running at 1/4 -3/4 throttle range and I rev around I default to the richest one that is most responsive .
Then I just fine tune the last 1/4 throttle with a 1/8 to 1/4 turn on the mixture screw if needed
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Post by drewzard6688 on Apr 30, 2022 9:13:41 GMT -5
Frustrated. I had the thing running pretty rich (spark plug is dark, way past chocolate brown, slow acceleration and burbbly exhaust note)) and welded a bung in my exhaust to run a wideband.
I know afr is kinda controversial on a 2t but the snowmobile guys use them to tune and monitor.
So my wot afr was super rich, 11.9:1 - 12.2-1.
And after a 3 mile wot run it seized.
I’m getting a little bit frustrated. I’ve been using the factory oil system and throwing a cap full of extra oil right into the fuel each fill.
The electric system stays on so I’m pretty sure it’s a soft seize. Will inspect the jug and piston when it’s cooled off. Maybe I should test the oil system, I had been riding about 20 minutes before the wot run though so I wouldn’t think there is any issue with the oil pump.
I did check ring gap before installing. The new top end/bbk has maybe 100 miles on it, I’ve been trying to dial in the tune the entire time.
Why would it seize while running so rich? If there was an air leak the o2 sensor would have caught it.
Glad my old top end is in good shape…
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Post by Zino on Apr 30, 2022 9:38:58 GMT -5
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Post by drewzard6688 on Apr 30, 2022 9:45:52 GMT -5
Always appreciate your wealth of knowledge Zino. Even after a good bit of clearance on the head my second temp sensor also bit the dust (main reason I decided to bite the bullet and get the wideband bung welded in) so I don’t know what my temps were. It seized while on an slightly uphill wot run, not after rolling off throttle. The 4 corner seize is visible but it’s ever so slight. Cylinder walls are still in good shape. Cold engine made 110psi compression. Pulled the oil pump line and kicked the bike over till it wept to verify there is oil. Will read the links you sent.
Edit. Yea. The others with stage6 street race issues have the exact issues I have. Will be looking to get a flex hone and give it a nice pass over and make sure the piston is good and clean as well. Funny enough I meant to buy the aluminum stage 6 and not the street race….
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Post by Zino on Apr 30, 2022 10:10:48 GMT -5
If you only got a few miles on your cylinder . Instead of a flex hone . You can just use ez off oven cleaner to dissolve any aluminum and clean it with a scotch brite pad . And then wash it with soap and water to wash away the oven cleaner.
Temps will drive up against the wind and up hill . A good way to test jetting is ride up a big hill.
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Post by Zino on Apr 30, 2022 10:36:53 GMT -5
2 options To get extra clearance honing will open the cylinder a little bit leaving the piston basiaclly as is .
Scotch guard and ez-off would require you to take the high spots off the piston to give you extra clearance .
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Post by drewzard6688 on Apr 30, 2022 11:24:14 GMT -5
I took a file to the piston and cleaned it up, seemed to solve the issues others had with the stage 6 streetrace. Polished it up after. Trying to source a flex hone today, the cylinder is really clean but based on the issues others had I wouldn't mind a bit more clearance. I think I will use the o2 sensor to dial in the carb to an acceptable, not quite as gurrgly burrbuly rich, and then just take it real slow the rest of the break in duration.
edit: Couldn't find a hone locally so I used scotch brite and made sure the cylinder was good. Need a new base gasket, once I cut one and reassemble I will update.
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Post by drewzard6688 on May 5, 2022 22:37:22 GMT -5
Update. Still in a bad state of tune. Very weird. The good: Filed and sanded piston clean. Used a fine scotchbright on the jug, cleaned all of it super super super well. Cut a new base gasket. Cold compression is 110psi with only about 5 miles of light test riding, so I think my bbk is still not fubar. I like the cheap-o amazon multi gauge I have, with simultaneous RPM, TEMP, and clock. It also logs max rpm & temp and has rpm & temp alert. The spark plug loop is crap and I've busted 2, so a trail tech CHT is in the mail. I took the part of the CHT still attached and shoved it in a cooling fin beside the exhaust port, slathered some jb weld on it. When the Trail Tech gets here I will compare temps and see if I can potentially use fin temps and then take the second gauge off after its dialed in.
The bad & weird: The wideband seems to work and be responsive. I can change the idle mix screw and see the wideband change almost instantly. Snowmobile guys use them on 2t stuff all the time, heck even turbo 2t stuff!
WOT seems to nearly peg the gauge at 10.9-11.1 afr no matter what main jet I used. from 80, 77.5, 75, 72.5 (50cc/YasuniR sweet spot, never had an issue on many many hour long rides to my friends next town over at WOT 47mph top speed,) 70.
I have a lot of jets from aliexpress. I used 5 different 75 jets just to make sure they were consistent. They were. I had a carb rebuild kit I used a while back that had a new pilot jet and needle, so I swapped it all back to the OEM parts I had kept. Still gets FAT RICH WOT. Even running a 72.5 jet its just burbbly 11:1 turning ~7000 rpm and never getting into the powerband. The rigged temp sensor says 240*F max.
I made sure the float was good too. Its not sinking, I would assume the carb would be leaking if it was.
The auto choke seems to work based on the idle afr.
I could grab the carb off the other vino...
I am getting tired, I will throw a new plug in tomorrow because the one I took out to check the compression was prettttttty wet.
I'm about to have a tach, 2 temp sensors, and a wideband on this thing, how is this thing kicking my butt?
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Post by Zino on May 6, 2022 8:06:36 GMT -5
11 to 1 with that big a jet range does not sound right . There is a noticeable difference from 80 to 72 for me by how it feels and sounds and temps .
After you are real warmed up When you are running wide open on a flattish road use this to guide you between jets .
Back down a 1/8 throttle to 1/4 throttle a few times after being wide open . This will richen you up temporarily . 3 things will happen rpms will rise This will mean main jet was a notchtoo lean Rpms will drop slow jet is right on Rpms will drop fast you are a notch rich
I would try this on the 72 and 70 since the afr shows them at the 11 to 1 .
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Post by drewzard6688 on May 6, 2022 8:26:26 GMT -5
Yeah the main jets seem to make a slight difference but not nearly the expected difference. I haven’t had it out of the neighborhood in a while but it’s getting plenty warmed up, and the o2 readings are consistent just super rich. I have about 1/4 mile slightly up hill I can wot run under load. The wideband is really nice to have, I’m just trying to get to around a ~12.5:1 afr, maybe a bit more rich for break in just to make sure it’s well cooled and lubed.
12.5-13.5:1 should be the good range for best healthy performance.
I’m tempted to throw a stock 64 jet in just to see what the wot afr is, it should be fairly lean with the displacement and pipe
When the trail tech comes in next week I will be more confident to take it back out into traffic to get to the quiet roads for wot testing.
The stock piston and jug on the shelf are looking more and more appealing. I had just dialed it in when I got the 70cc. With the o2 setup I could probably get a little more performance too…
Update: Ok got a new plug in and a 70 main jet. The rpm is back, the afr was about 11.9:1 wot. 1/2 throttle is burbbly but says it’s 12.5:1, but its lazy until I crack the throttle and get the speed up. Temps with my rigged sensor stayed ~250°f.
Will probably gather all of my 70 jets and try them. I’d like a little less fuel wot. It’s still baffling to me how rich it’s running with the same jets that the 49cc bore was a tad bit rich with.
I’m going to say that the soft seizing was from too much rpm too much wot without about clearance or break in time.
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