Go Go Sundiro! 70cc Stage6 Sport Pro MKII build

[lordverminaard]

No restrictor that I saw, unless this pipe has another one somewhere other than right at the flange.

Thanks,
Brendan

[oldgeek]

Just skimming over this thread a bit. You have a PHBG 21mm, stock air box, no snorkel, holes added (how many and what size?)

Pilot should be around 42-45 max
slide 40?
W7 needle?
Main jet Around 95-105

The PHBG is kinda hard to tune BECAUSE it is so tunable. One thing that got me is the mixture screw, IN is LEAN, OUT is RICHER. Also make sure the bowl vents are not capped.

From video it sounds pig rich down low.

[190mech]

Sounds rich to me,drop the needle(raise the clip) and see how it acts,iggy timing sounds retarded too,have you checked it with a light?Gotta get some stiffer clutch springs too...A quick sanity check would be remove the airbox and see what it does,that'd lean the crap out of it...

[spaz12]

First thing I noticed... You're not the same person as the guy in your avatar picture. False advertising? I was mildly disappointed since I thought for sure we had an honest to goodness celeb on the forum. Just sayin

Does the Dellorto clone come with that silly copper disk that's held on by the main jet? If it has one, get rid of it. They're there just to frustrate you and if they are installed upside down they will cause the symptoms you're having now. Ask me how I know.
Sorta curious if you did a leak down test on it as well?

[lordverminaard]

Jul 18, 2017 16:36:47 GMT -5 oldgeek said:

Just skimming over this thread a bit. You have a PHBG 21mm, stock air box, no snorkel, holes added (how many and what size?)

Pilot should be around 42-45 max
slide 40?
W7 needle?
Main jet Around 95-105

The PHBG is kinda hard to tune BECAUSE it is so tunable. One thing that got me is the mixture screw, IN is LEAN, OUT is RICHER. Also make sure the bowl vents are not capped.

From video it sounds pig rich down low. 

Thanks for the replies!  

There are 3 holes in the back, about 3/4 of an inch each.

I have a 40 slide, and W7 needle.  I started with a 42 pilot and 95 main, it literally wouldn't rev past 1/2 throttle at all, (it would even die if I kept it held in) and didn't have enough power to go up a very slight gradual hill.  Pulling the plug after that, it was very light and white in spots.  It was also making that gasping "bwaaaaaah" sound when snapping the throttle, like in the video that 90GTVert posted on lean vs. rich.

Thanks again for the help.
Brendan

[lordverminaard]

Jul 18, 2017 16:39:24 GMT -5 190mech said:

Sounds rich to me,drop the needle(raise the clip) and see how it acts,iggy timing sounds retarded too,have you checked it with a light?Gotta get some stiffer clutch springs too...A quick sanity check would be remove the airbox and see what it does,that'd lean the crap out of it...

Thanks for the tips- I dropped the needle two clicks to 2nd one down from the top.  I also pulled the airbox to see what happens.  (initially, with 42 pilot and 95 mains, it wouldn't run at all without airbox)  With airbox pulled, it started easier, and was better down low when I had the mixture screw out a lot (3 or 4 turns out) but it made the laggy/slow revving worse past half throttle.  If I leaned out the mixture screw to a "normal" position (2 1/2 turns out or so) the idle would hang a lot, and it would lag much sooner in the rpm range and even would not rev at all under full throttle.  

I don't have a timing light but I think a friend has one I can borrow.  How would the timing be out if I didn't change anything and the timing isn't adjustable?  Just curious how that could be off.

I put the airbox back on, without changing the mixture screw, I had to adjust idle (idle would still hang a bit) but it felt really good up to 1/2 throttle.  I rode it around the block again, and I could go from stop to 1/2 throttle and it felt basically as fast as it felt when it was stock at full throttle.  3/4 throttle, nothing else really happened, and full throttle would still bog and gasp.  I pulled the plug after this and it was very light and white on the electrode.  

Also, I was trying to memorize the sound of the max RPM that I could get it to while riding, then tried to match that on the stand, and it's like, barely 1/8th throttle, if I had to guess maybe 4500 rpm.  The CVT has fully shifted at that point too.  This cylinder is supposed to be good to 13k rpm so I think some CVT mods are in order.

I still feel like my pilot is a little big, but it still seems to want more in the main jet.  Whenever I richen up the mixture screw to crazy levels, it is rich as hell at the bottom but the lagging seems to be better up top.

Thanks again, I really appreciate the replies.
Brendan

[lordverminaard]

Jul 19, 2017 0:27:57 GMT -5 spaz12 said:

First thing I noticed... You're not the same person as the guy in your avatar picture. False advertising? I was mildly disappointed since I thought for sure we had an honest to goodness celeb on the forum. Just sayin

Does the Dellorto clone come with that silly copper disk that's held on by the main jet? If it has one, get rid of it. They're there just to frustrate you and if they are installed upside down they will cause the symptoms you're having now. Ask me how I know.
Sorta curious if you did a leak down test on it as well?

Haha, sorry to disappoint.  Although if the Dude worked in IT and didn't smoke pot, we would basically be the same person, lol.

I've read about that disk, and I'm still not sure what it is, but when I had the carb apart to clean, I didn't see anything between the main jet and the emulsion tube or the needle bushing part.  So I guess it doesn't have it?

Also I didn't do a leak down test.  Probably should have, but when I had it apart, I didn't really see any evidence of the case leaking anywhere but I don't have the equipment to do it.  I didn't split the case or remove any seals so I was just crossing my fingers that it was ok, lol.

thanks,
Brendan

[oldgeek]

IMO, You are getting too much air, which makes it harder to get tuned. I would close off all of the holes you drilled leaving just the hole where the snorkel was. For me the PHBG has been particularly hard to tune when using a uni or free flow type filter. Also your gas mileage will be much better with an airbox vs free flow.

[190mech]

I had to throw iggy timing in the mix as you didnt get many miles in stock form before the mods..Your sluggish throttle response and wet plug could point to rich conditions at certain throttle settings OR a weak a** retarded spark..Kitting an unknown engine is a crap shoot,no before data points to calculate from..Keep poking at it,you'll be doing wheelies and getting the old folk in the neighbor hood mad soon!!

[lordverminaard]

Jul 19, 2017 19:11:20 GMT -5 190mech said:

I had to throw iggy timing in the mix as you didnt get many miles in stock form before the mods..Your sluggish throttle response and wet plug could point to rich conditions at certain throttle settings OR a weak a** retarded spark..Kitting an unknown engine is a crap shoot,no before data points to calculate from..Keep poking at it,you'll be doing wheelies and getting the old folk in the neighbor hood mad soon!!

Well, now that you mention it, the bike was more or less behaving the same way when it was stock- bogging hard at 1/2 throttle.  I have replaced the carb, cylinder, spark plug, coil\wire... the only thing that was left over is the CDI and flywheel\stator.  I have one of those "Racing CDI" units from ebay but not installed as I assumed they can cause more issues than they solve.

Also last night, I taped up the holes I made in the airbox and tried it- it was better, and actually let me go full throttle without bogging.  It was still very low on power though.  I then pulled the main jet and put the 95 back in.  I had drilled out all my pilot jets so I didn't have one smaller than what was in it, (56) so I turned the mix screw in almost all the way lean.  Started up nice and easy, but the bogging was much worse at 1/2 throttle and wouldn't even go full throttle at all.  Turning the mix screw out a couple turns made it sputter down low but it was slightly better at half throttle and let me go full throttle briefly before cutting out.

So I guess I will borrow a timing light and see what is going on with that.  Also I pulled the cvt cover and verified that yes, the CVT starts to shift immediately after the clutch engages and it is fully variated (or at least very close) at less than 1/4 steady throttle.  Gotta fix that I guess.  Also I would love a CHT unit, that might make tuning easier.  Not sure.  One of the reasons why I like tuning fuel injection so much is that you have all kinds of data to go off of, carb tuning seems like more shots in the dark sometimes.  I think that is why I am still not real comfortable doing it, but hey, gotta learn sometime I suppose.

Thanks,
Brendan

[lordverminaard]

I've made some progress!!!!!

I drilled out the roller weights from 7 grams to 6.5. Not a big difference I know, but I was trying to do it quickly. I also removed the tape over the airbox holes, and drilled out the main to 136, up from 126. Fired it back up, and it ran so much better. After tweaking the mix screw, it will pull soundly from idle to WOT, with only a slight burble in the low-mid RPM range, which I think I can live with. If I steadily go from idle to WOT a little slower, it will rev cleanly all the way up. I rode it, and the roller weights made a slight difference in RPM but that slight difference helped. It still won't go too fast up a hill and I can't rev it out on the flat due to the CVT shifting way too early still. I also think the stock contra spring is fatigued, when I was re-assembling the CVT, I could easily spread the rear pulley with one hand when I was putting the belt back on. I don't think it should be that easy, lol.

Another issue to be addressed is that the stock CDI is hitting a limiter, and it sounds like the engine wants to rev even more. I have a "new racing" cdi to install at some point but it's not a show stopper right now.

I managed to borrow a timing light from a friend, I will check ignition timing too and verify it is good at some point.

Going to order contra springs and probably clutch springs soon, then I will dial in the roller weights and I should finally be getting somewhere at that point.

Thanks everyone for the help so far!
Brendan

[lordverminaard]

More stuff happening, and finding out some fun stuff about this scooter. I decided to wire in my "new racing" CDI but the wiring for this scooter doesn't look like anything I have found online at all and doesn't match the CDI wiring. There is a handy wiring diagram in the owners manual but it didn't match either, lol. There was another diagram in the manual for the 90cc model and sure enough it matches that one. I wired it up and fired it and while it might be my imagination it seems to be running a lot better and a lot of that mid-rpm bog was gone.

I then drilled out the rollers to 6 grams and gave it another try, much better still, but the variator is still shifting way early but I know I am on the right track now.

Speaking of variators, I was searching for parts and was comparing the different sized variators, and after doing some measuring, this scooter also has the 90cc variator setup, it has the larger drive boss, and the 90cc gears. Despite having the larger output shaft it had a 10mm wrist pin. I know for a fact that the engine was a 50cc though but I would even bet money that the case is probably clearanced for the 90cc crank.

Once I have a little extra money I will order a new koso variator kit, which comes with a bunch of different weights, new clutch springs and torque springs and I think that will get me on my way. Also going to go down a couple sizes on the pilot jet, having trouble starting it when cold and I think that will crisp up the off-idle revs some.

I also tied up wires and clamped hoses in preparation for "finalizing" everything. Probably won't update again until I get my CVT stuff.

Laters,
Brendan

[lordverminaard]

Another update, ordered my koso variator, which includes a ton of weights, complete variator, 1500 contra and clutch springs. Also probably going to register the scoot this week.

It was running so much better with the "New Racing" cdi, that I decided to re-assess my carb tuning. I knew the jets were too big, but I didn't have another pilot jet to try since I had drilled out the ones I had to a very large size. Found one of my Keihin CV carbs from my Kawasaki laying around and examined the jets, and it has a complicated 5-jet setup but one of the slow air jets was a 40 and very similar in size to the PHBG pilot jet. So I drilled that out to a 47 and stuck it in there. Noticed an immediate improvement in idle and 1/4 rpm blips, so I experimented with main jets again and arrived at a 107. The scooter was running good enough even with the variator shifting so early, that I took a nice ride in the neighborhood for a couple miles, and other than launches being slow, it ran great! I didn't have much road to get crazy with it, and the speedometer doesn't work but I felt like it really starts to get in the beginning of the powerband at around 40-ish mph.

I'll try and get a video of it running again if I can figure out how to mount my phone to it, haha.

Brendan

[lordverminaard]

Package tracking says my variator stuff hasn't left China yet.... grrr. So I put most of the panels on it and gave it a bath. The pipe won't allow the side and rear fairings to work so I guess I have to run without them until I get a different pipe maybe. But it doesn't look too bad considering.









After this, it wouldn't start, or it would start and run like crap\die out from time to time. Figured out it was water in the ignition switch. Will make sure to store that in my memory banks for future reference.

I have been having other starting issues with it as well, it will fire on the first kick but then quickly die- within 1 or 2 seconds. Then it won't start at all unless I hook up a battery and crank the electric start for a while, or spray some carb cleaner in the airbox and kick it a few more times. I watched one of 90GTVert 's videos where he tested CDI's and saw that they can cause hard starting issues, so I swapped it back out for a stock CDI and it's slightly better but still starts pretty hard when cold. I know the choke is working because I can pull it when it is running and notice an immediate difference in how it runs. When it is warm it fires up right away without the choke usually.

Rode it around the neighborhood a little more and did another plug reading, still looks bang on. I managed to get my phone mounted so I could use a GPS speedometer, and at around 37 mph it starts to really get into the powerband and pull hard, but I never had enough road to pull it much farther than that. I need that variator\clutch\contra spring ASAP!!!

Brendan

[lordverminaard]

Never mind about the starting thing, I cold started it a few times over the past few days and it started first kick, lol. Oh well!

Brendan