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Post by oldgeek on Sept 30, 2023 20:57:10 GMT -5
Spent the better part of the day trying different tunes on the PWK carb, without making much progress. I am scared I am going to toast this setup before I find a decent tune. I guess the PWK carb is not the best choice for an all range tune, it can be set up pretty easily for WOT and likely mid but low speed always seems to be lean or pig rich for me. Possibly I need a more restrictive air box or one of the venturi dividers I have heard about.
On the short side road near my shop I saw 75MPH (edit: battery in TT Vapor died and it lost my tire size settings, actual speed so far is about 65 MPH) It has plenty of torque on the low end when I can get the carb to clear up, and it pulls nicely on the way to the top. I am scared to let it rev above 11K or so with the stock flywheel, I dont really know how fast you can safely spin the stock stuff. I dont know where I am going from here, but this setup will be a runner if I can find a decent tune. All suggestion welcomed and appreciated.
I am going to try to do a video tomorrow if I can.
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Post by oldgeek on Oct 1, 2023 19:25:25 GMT -5
I updated my previous post to correct my top speed to 65 mph so far. The backup battery in my trail tech Vapor had died and reset my tire size info to factory settings so my speed was off quite a bit. I guess it was wishful thinking on my part Lol, I really think it easily has 75 mph in it but I am not there yet. I am using the same CVT components I used on the 103cc build so at least I am not having to tune the CVT and the carb at the same time.
The carb tune is getting better but it has certainly been a struggle. The low speed jet drives me nuts, a 50 is a bit rich and if you pull the choke it dies. A 48 is a bit lean and if you pull the choke it runs great through the whole range. The low speed screw seems to have little if any effect. I think my current needle is better but temps are up around 145 F now. I have no clue what temp this cast iron LC kit should run.
I also had a main ground wire come loose that made me think something had really broke. When the wire came loose it ran really rough and backfired twice really bad. I pulled the intake off because I thought the reeds were surely shattered but they were fine. The plug also looked good and the flywheel had not slipped. I suppose the CDI did not like having no ground connection and could not fire correctly. I also checked compression, it is around 150. So not as high as I would like it to be but not horrible.
On one run I unexpectedly pulled the front end up hard, I did not like that feeling.
The Fall Harley rally begins this week, there are already a few here. The weather forecast for this week is very good so there should be a huge turnout. We should be slow this week at work so I am hoping to get the scoot tuned up enough to take it on a real ride and mess with the Harleys.
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Post by 190mech on Oct 2, 2023 7:15:43 GMT -5
Is it a knockoff carb and jets? If so that may be your jet problem as numbers on the jets dont mean much! That carb should tune well..
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Post by oldgeek on Oct 2, 2023 13:46:58 GMT -5
Is it a knockoff carb and jets? If so that may be your jet problem as numbers on the jets dont mean much! That carb should tune well.. It is the Polini branded PWK. The jets I don't know about but I have jet drills to check some sizes. |
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Post by oldgeek on Oct 3, 2023 20:00:42 GMT -5
First off I fixed some roadworthy problems today. The blinkers needed a new flasher module before they would work and both rear LED brake lights were out. Then on the very first tuning run on the short test road by the shop I ran out of gas and the gas cans were empty so I made a trip to the gas station. I got that all sorted but then had to go do some service calls. I finally got to do a couple tuning runs and was getting nowhere at all. So I sat down to really think about what was going on. I decided to drastically change carb components cause I had nothing to loose. I went from a 151MJ to a 140MJ, a 45PJ to a 40PJ moved the needle clip from the top to the middle and went with a leaner slide. I also lightened sliders up a little moving from a total of 40.5g to 39g
To my surprise it worked out well, something is still making just off idle rich at times but it is not as near bad as it has been. I felt good enough to take it on the longer test loop for the first time. Top end in the video was 69 MPH which agreed with my Trail Tech speedo. It has more but to be honest I was a bit scared just going 69. Scooter sounds change around 65 MPH or so, for me the gearbox sounds become very noticeable and then I started thinking about the center stand which is rubbing the tire ever so slightly. The center stand is also vibrating against the case making a strange noise, which it has done before, I thought it was knock on the 103 motor Lol! I will get it all sorted soon and post another video.
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Post by 808ministroke on Oct 3, 2023 21:11:04 GMT -5
Nice job man thanks for making videos I love watching 4 members post riding videos it's almost the closest thing to riding yourself and it was fun just watching I'm glad you finally got this build together.
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sinfull
Scoot Enthusiast
Posts: 413
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Post by sinfull on Oct 4, 2023 1:40:14 GMT -5
Record the highest Temps you see at wide open throttle, extended runs, on my air cooled builds I stay usually above 300 ish, off throttle I want to see a almost immediate 20 to 30 temp drop, that should get your jetting close, never did a LC engine but I would be after a decent temp drop off throttle, and if you are still worried about it, pull the head and check bore, you will know immediately if you are running lean, between the bore and spark plug you should be able to know exactly what is going on afr wise.
Jet size I never really worried about, master 2 stroke Joe can tell me what his bike runs all day in his city at sea level but meant nothing to me in my city at 5k feet above sea level with dry no humidity air, go by what the spark plug and the bore say, they know best 😀
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Post by oldgeek on Oct 4, 2023 18:51:23 GMT -5
I made a stop for the center stand from some type of urethane block I had laying around, no more tire rub or rattles. I got the carb to what I thought was decent enough to take a ride down the strip just before noon today. It actually ran really well except it would load up 50% of the time when I stopped for a light, then take 5 or 10 seconds to clear out and let me go again.
I changed many different things one thing at a time but it only seems to stay the same or get worse.
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Post by 190mech on Oct 5, 2023 16:50:55 GMT -5
Could be the float level is a bit high or needle and seat are not seating properly causing a higher float level at idle..Wow, that reads kinda confusing!
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Post by oldgeek on Oct 5, 2023 18:14:08 GMT -5
Could be the float level is a bit high or needle and seat are not seating properly causing a higher float level at idle..Wow, that reads kinda confusing! It could just be me doing something stupid, in my current state of mind. It may even be the cheap Polini PWK knockoff carb I am using, I dont think I ever got it right on the 103cc before I fried the piston using it. I tried a couple more changes today no better. I know there is a slight air leak at the 3 of the studs that hold the cases together, the sealing washers I used did not seal properly. So this afternoon I pulled the three nuts back off and used some airseal sealant and the sealing washers to hopefully end that air leak. I will also check the float like you said, I could have easily bent it during one of the many changes I made. I am running a BR9HIX plug I wonder if I need a different heat range? I was thinking you would use a hotter plug on an LC motor but that does not seem to be the case on Brent's LC motor IIRC. If I do not get it sorted out pretty quickly tomorrow I am going to try the 21mm Dellorto. I am 120cc and 11K tops I bet it would work fine and be more street friendly. It may be time to repair the piece of a peace pipe and give it a try. I saw SAMODEL recently cut a TWH pipe apart that is just like mine. Inside it is basically just a chambered pipe with no stinger. It may be similar in performance to the PG short I LOVE (not) so much. |
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Post by oldgeek on Oct 5, 2023 19:25:12 GMT -5
I just saw another recent video Samodel did where he dyno the same TWH pipe I have, on an AC 120cc kit. 12.8 peak HP @ 10350 RPM
Pretty much same RPM I feel the strongest pull. I also noticed no power on the graph until 6-7K So I think I found my problem LOL ! My clutch is coming in to soon! I am such an ID10T at times. That's what I get for taking a couple years off from tuning.
So should be no surprise the pipe performs very much like the PG short pipe, the TWH is just made for a bigger motor.
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Post by aeroxbud on Oct 6, 2023 3:13:22 GMT -5
That's the low end bog then. Let's hope it's so easily sorted.👍
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Post by 90GTVert on Oct 6, 2023 8:20:22 GMT -5
I got the carb to what I thought was decent enough to take a ride down the strip just before noon today. It actually ran really well except it would load up 50% of the time when I stopped for a light, then take 5 or 10 seconds to clear out and let me go again. I changed many different things one thing at a time but it only seems to stay the same or get worse. I can't say that I understand why, but when I go to the beach I can't seem to keep my idle settings right. I may adjust the mix and speed so it treats me well, but if I ride for long it will stop working well or sometimes feel random. I have learned that I need to be careful with touching the throttle when stopped. I get paranoid that it's going to cut out... especially at car and bike shows where loud stuff is around and it's tough to hear. That makes me hold the throttle a little to be sure RPM is up and that can be enough to get me into the rich zone just off idle for me. The area we need to cruise at basically no throttle and stay nice and safe. I could be a little too rich there, but generally it works well so I don't have a great desire to attempt to lean it out and possibly lean other areas a little too much. Best bet for me is try to get the idle settings so it's safe to leave alone and try not to touch the throttle when stopped... unless blipping to make my presence known. lol Anyway, I guess if all of your other stuff doesn't do this then it's yet to be solved. I've always wondered if an area like Ocean City which is a strip with ocean on one side and bay on the other could be so affected by winds off of the waters and such that it does change conditions more than when I'm home in the corn fields. You just have one big coast, but still perhaps some effect of winds changing around and blowing more from land or sea could be in some small part responsible? Sounds kinda dumb when I read it, but I think Ryan has also seen that idles seem more sensitive at the beach and I'm not sure what else it would be. I definitely get changes with other riding, but not quite like this. I went to TN 10 hours away in the mountains. Adjsuted the idle settings once for the change and I don't think I messed with them again. I drive 70 miles to the beach and adjust it 45 times in a few hours. Hopefully some more "free" settings in the CVT will zip you right past any bog. If it's only when throttle is applied and idle stays the same when untouched, then what I said prob isn't as relevant. BTW, simple solution till it's figured out may be to blip it below clutch engagement while stopped to keep it cleared out. |
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Post by oldgeek on Oct 6, 2023 19:35:57 GMT -5
I tightened up the S6 clutch as tight as it would go with the red springs, It was already pretty tight. It did seem to help some and I got it back running as good as I have had it so far, but the bog is still there sporadically. Again, I tried quite a few different changes but no real improvement. I found a tuning chart for the carb and I it is helping me as I study it more. There are even more tuning considerations for these carbs than the PHBG's. I am gong to order some needles that are different than the ones I have. Looking at the chart, there is a "straight dia." of the needle that I want to focus on a bit. Most of the needles I currently have seem to be better suited for bigger motor applications. I may take a break from tuning until the new needles get here, as I am kind of burnt out ATM.  |
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Post by oldgeek on Oct 6, 2023 20:02:27 GMT -5
Anyway, I guess if all of your other stuff doesn't do this then it's yet to be solved. I've always wondered if an area like Ocean City which is a strip with ocean on one side and bay on the other could be so affected by winds off of the waters and such that it does change conditions more than when I'm home in the corn fields. You just have one big coast, but still perhaps some effect of winds changing around and blowing more from land or sea could be in some small part responsible? Sounds kinda dumb when I read it, but I think Ryan has also seen that idles seem more sensitive at the beach and I'm not sure what else it would be. I definitely get changes with other riding, but not quite like this. I went to TN 10 hours away in the mountains. Adjsuted the idle settings once for the change and I don't think I messed with them again. I drive 70 miles to the beach and adjust it 45 times in a few hours. Hopefully some more "free" settings in the CVT will zip you right past any bog. If it's only when throttle is applied and idle stays the same when untouched, then what I said prob isn't as relevant. BTW, simple solution till it's figured out may be to blip it below clutch engagement while stopped to keep it cleared out. I think the problem may be the style of riding being done at any given moment. IMO a truly seamless tune is necessary for riding on OC strip or the blvd. There is a lot of stop and go and we are in many different throttle positions in those situations. One slightly lean position or a rich position can set you up and make you off for a moment. A fairly seamless tune may get you by in the mountains or country riding and never be a problem but down in OC it may show its self. Anyway thats my theory for what its worth. I have tried so many setups on this carb and getting much of anything to transition smoothly has eluded me. I can get it great off idle but then a hideous lean spot immediately after that. I can get it decent feeling the whole range but then it loads up coming off a medium run. There are peaks and valleys to be flattened out all over the place and 9 or 10 variables to get it all done with. LoL |
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