Roughhouse 70cc problems

[luvscooters]

Let me first start off by saying hello to everybody. Had motorcycles my whole life and the past couple of years also enjoyed various different scooter models. Recently I purchased a year old rough House and decided to upgrade to a 70cc. I purchased the ncy kit that everybody sees advertised. Removal of the body work got that stripped down and had the head removed clean the surfaces up put the piston on the circlip was a pain in the butt also but after watching some videos everything went back together. I used assembly lube, the light coating of the Honda sealer was used on the block in the head. Installed the ncy expansion pipe everything went together pretty easily and it fired right up. I was running a 42 pilot and a 95 main as recommended they give you a variety of jets main Jets anyways up to I think like 110 or so in this little box. At this point in time I still had no adjustment on the fuel air screw it was stock and the scooter ran terrible it would idle but had no power whatsoever so I dug out the little epoxy and took a Dremel and cut a slash groove in the fuel air screw and it was actually turned all the way to the right it was bottomed out from the original carburetor setup. So I backed it out a little bit and began getting some responsiveness and crispness when blipping the throttle. And ran it up the street back down about an eighth quarter throttle you could feel the difference of the torque of the engine from 50 to 70 just a little bit of gas and it would accelerate whereas before you'd have to hold it wide open to get it to move. I brought it back home and I put in 100 main jet just to be on the safe side started it up ran it through several heat cycles and decided to take it up the road this time with the 100 it wouldn't get over about 5 mph it was just so rich there was nothing that could burn that gas it was just literally raw gas I could tell was coming out. So I brought it back home and put the 95 in and took it up the road and gradually giving it a little bit more fuel a little bit more throttle and then I got a soft sieze. So I brought it back home wait a little cold I did a compression test and I don't know if the gauge I have is accurate but it read around 125 lb of pressure. Yesterday the humidity had dropped considerably than the prior days and I understand the correlation you know water in the air doesn't burn and less humidity and engine is going to run better. So I decided to take it around the block and gradually began opening it up a little bit more probably around 45 miles an hour indicated.. the around the block run is maybe a mile and a half total distance or so.. after I would run it three quarter throttle or so I would chop the throttle for a second or two and then I'd gradually roll back on to about a quarter throttle and build up speed and then I would chop the throttle so I was not holding it wide Open ever and I was not 3/4 throttle for more than a couple of seconds Max. When I turned on to one of the side streets that had a speed limit posted a 15 mph I was just above idle rolling along and it soft siezed again. Scooter came to a stop hit the start button at fired back up I know exactly what's happened. To say that I'm pissed off and frustrated is an understatement at this point. I did add incidentally probably an extra ounce of 2-stroke oil to the fuel tank prior to taking it out the second time. So here I am Sunday morning trying to figure out do I just put it back to stock and call it a day and sell it because I'm frustrated and wipe my hands clean take the loss and move on. Or do I buy another top end kit put it back on to be faced with the same issue because obviously something's not right 95 seem to run well it seemed to me slightly on the rich side actually 100 main jet was impossible to run it was far too rich. Prior to till going out yesterday I did buy one of these cheap Chinese knockoff carbs when I took it apart I found out that the needle jet actually had three slots so in the back of my mind I was thinking okay if I run the hundred main I can lean out the needle jet by moving the clip. But I never got that far to do the swap. I'm not opposed to buying another top end you know for 150 bucks and cutting my hands all up putting it on but I just don't want to have to wind up with the same results that had happened to me the first time. So what are your thoughts?

[luvscooters]

After finishing up my morning coffee I decided to go downstairs to see how bad the compression is in the scooter. I've had two soft sieze. I did not check the compression after the build in retrospect I guess I should have done so nor did I check the compression of the stock scooter because it was running perfectly fine and again in retrospect I should have done so because this will have put my mind at ease if my gauge is accurate. Because if it's off it would lead to an erroneous decision with regard to how much compression the engine is actually putting out and what is the health of the piston rings to cylinder walls. The first time I had the soft sieze. I was only running quarter to half throttle going down a little bit of a hill RPMs picked up fine engine was running good I was probably doing 45 or so miles an hour and when I rolled off the throttle that's when I felt a little surge and that's when the engine came to a stop. So I was right by my driveway pushed it into the basement way to look cool pulled the plug the plug was actually indicating a rich condition it was certainly not ceramic white it was closer to a very very dark color indicating there was plenty of oil and plenty of fuel going in. So hooking up the compression gauge I got results holding the throttle wide open and initially using the electric start and following through about 10-12 kicks of the kickstarter right around 125 1:30 it's hard to actually read because well when you look at the gauge you'll see what I'm talking about. And moments ago I hooked up the compression gauge and did a test and it appears to be virtually the same numbers as the first time. I took pictures but I don't know how to post pictures on this forum. But it looks like 127 128 maybe win a 129 it's just it's a big needle on the gauge it's not 1:30 but it certainly isn't 120 the bottom line is it appears to be exactly the same as the first time I checked it. So now I'm left with this quandary what do I do?? Again I'm running a 42 pilot I'm running a 95 main I have an adjustable fuel air screw and I know that's only the first 8th to quarter of the throttle and it's not immediately snappy which to me indicates it's still on the rich side which is how I wanted it set up. The scooter is slow to accelerate for the first one two seconds even when you're half throttle you know three quarter throttle but immediately after a couple mile an hour it gets on the pipe and it's immediately right up to 40 miles an hour very very quick. And I'm not holding it wide Open I'm kind of giving it the throttle to get it up to speed and then backing off to a quarter third throttle where it feels good it's able to roll up a hill accelerate up a hill and you feel it pulling. the only thing that I did do that I didn't disclose is the stock air box I removed the rubber tube and I cut out the plastic panel that the rubber air inlet mounts to so I'm still running the stock air box I'm still running the stock filter I just opened up the inlet so that more air would be coming in and that seemed to help quite a bit with the 95 main jet when I initially ran it with the stock rubber 90° air inlet it was extremely rich so that extra little bit of air helped it out throughout the entire power curve. I have extra oil added into the gasoline so I know it's getting plenty of oil but obviously the engine's getting hot the weather out here is 85° or so yesterday I think when I took it around the block it was maybe 80 so it wasn't a scorcher temperature wise. That's a 202 but something obviously is not right because I've had two issues with it so far where it's soft seize and shut off .

I don't know how to upload pictures to the site so I uploaded it to another one and here's a link so you can see the results of the compression test on the gauge.
ibb.co/0MyPXQ1

[aeroxbud]

[aeroxbud]

Just copy the BB link and paste it in the reply box.

I think by adjusting the mixture screw, and putting holes in the air box. You have made it very lean at part throttle. You probably need a different needle, or at least make the needle you have richer.

[luvscooters]

What I wanted to do was to test the accuracy of the gauge that I have so I took a 25cc weed wacker 2-stroke that does not have a compression release and I screwed in first using the hose with the adapter to take a reading and I got 120 PSI. Then I removed the adapter and the hose and I went straight with a metal direct compression fitting directly to the gauge so there's no coupling it's basically a one-to-one connection and the results were 150 psi. So this led me to believe that the little adapter that connects to the hose I've got a leak in there ever so slight despite the o-ring still being in perfect condition. So what I did was I removed the adapter and that's a 14 mm adapter which is the thread size that a plug and to my surprise the adapter size that I was connecting to the hose which would connect to the gauge that's also a 14 mm so I eliminated that middle man connection there's no reason for it and I threaded the hose directly back into the cylinder head of the scooter. Wide open throttle kicked it about 15 times and now I'm reading over 130 PSI and you can see from the picture.

ibb.co/0281JtT

So I don't know how much damage has been done to the scooter from the two soft sieze. It starts right up so that's not an issue and it's reading over 130 PSI and I tested it multiple times.

I do have an idea and I posted this earlier I wanted to get some feedback. I bought a cheap Chinese carburetor that's made for the rough House and it has an adjustable fuel air but I've since adapted my stock one so it has an adjustable fuel air the difference is is the stock needle jet on the slide is not adjustable well I've got shims that I have little tiny washers but within the Chinese carburetor when I took it apart that slide needle has three settings and you can remove the little c clip so what I was thinking. With a 95 main jet if I enrichen the stock needle which means I would move it down one clip cuz there's three and it's in the middle so that would enrichen the mid-range. So what are your thoughts about doing that or putting in the hundred yet which was so fat the scooter couldn't get out of its own way I mean I'm talking five miles an hour it was bogging you couldn't get it to move. If I put the hundred jet in and then lean out the needle by moving it up..
And again what I did to the airbox I didn't drill holes into anything you have the rubber 90° neck that's pushed inside of the air box base and that is where the air comes from in order to fill the air box which then circulates through the filter all that I did was I removed that rubber 90° neck in the plastic support that that rubber intake gets shoved into I cut out so I'm letting in more air but it still must pass through a sealed air box and the stock air filter assembly.

[luvscooters]

ibb.co/0281JtT

[aeroxbud]

If in doubt I would just pull the cylinder off to have a look. Often it's easier to pull the engine from the scooter to work on. It's only a couple of bolts.
I Jack the scooter up. Then remove the shock mount bolt, and engine bolt. Undo the wiring. You can then slide the engine round enough to leave the oil pipe attached.
With an air cooled scooter it's very easy.

When you put the circlips into the piston. Do the hardest side to reach on the bench. Before fitting the piston to the crank.

[luvscooters]

This is the adjustable needle from a Chinese knockoff called a kipa, and this is 100% identical to the rough House carburetor that it was removed from except that the little Chinese knockoff has an adjustable fuel air screw and again I've already made mine adjustable by cutting a groove so what I'm going to try initially is enriching the needle and I need to confirm it but I'm pretty sure if I move the clip lower because it's in the middle clip now that will raise the needle up more which provides more fuel at partial throttle.
ibb.co/HxcVS85

[190mech]

That is correct. Part throttle is controlled by the jet needle, thats where engines seize the most due to tuning only the main jet and pilot..

[luvscooters]

That's really interesting because I would have thought that wide open is where you're getting a problem being lean and I read similar builds and obviously the altitude of where you are in the ambient Air temperature the time of year season can make a big difference on your jetting I get that. That being said I noticed a lot of people with the same exact builds running 110 main jet and I don't know how they get away with it unless it's again 40° outside air temperature and it's a much denser charge of air coming in so you can use more fuel. At any rate I removed the clip on my cheap Chinese knockoff needle jet down one there's only three positions it was in the middle and I installed that needle jet and slide into the factory carburetor started it up let it come up to temperature I didn't adjust fuel air screw at all I kept at the same. And I ran it up the road and back so about a mile to the turn and then back home so a 2 mi quick run. It's really not a fast scooter off idle to until the variator starts to come into play in the belt starts to move from the speed of the engine and then it climbs very quickly to 40 mph significantly faster than it was a 50cc 50c would take me hundreds of yards 200 yards maybe off hand pick a number to get to 40 miles an hour. And that was de-restricted otherwise bone stock and I'm 240 lb. I did run it wide Open but for a very brief period maybe 2 seconds 3 seconds tops and it pinned the needle 50 and it was still climbing and I chopped the throttle because I only have on this build maybe 15 miles total. When the scooter was de-restricted stock going downhill holding it wide Open I hit and these are 3- 5° grade downhill some of them mid fifties mpg which is plenty fast for a big guy on a small scooter. And that's using a GPS from my phone so I know obviously it's accurate. I don't want to do the same run again cuz I'm not really concerned about trying to hit 57 or 60 I'm more interested in having the ability for it to maintain 35-40 miles an hour climbing hills on road so I don't get run over by cars behind me. What I think I may try and not today is going back to the hundred jet I don't think there's anything in between a 95 and 100 in the little kit that came with this stage two package. And removing the needle jet and leaning it out putting it at the highest setting right now it's the lowest setting so I want to see if that makes a difference or if it's still way too rich. And if it's way too rich then I would default back to where I am right now which seems pretty good.

[sinfull]

When you did the cylinder did you presure test after to make sure you don't have any air leaks ?? Intake all sealed up and tight ?? Did you check squish or stack base gaskets or something different ??

You mentioned having sealed up mix screws and non adjustments and you switched carbs, same size or bigger carb ?? The new carb is adjustable ??

You can try and see if the airbox is just choking the carb, run the 100 without the airbox and see if it helps, larger carb and pipe, airbox could choke the carb since you are now moving alot more air than the airbox allows.

Have had 1 bike that could not get tuned without the airbox, another that would not run with it, same setup on both. Always say 2 stroke are wierd like that, they want what they want and doesn't matter if everyone else is running x jet and your bike will run on y jet and not run on x jet. They just wierd sometimes

[luvscooters]

There's no leaks when I did the compression test for about 5 minutes it held over 130 whatever it was 132 133 PSI there was no reduction at all so I know they had the work on that is fine I've worked on small engines for many many years so it's not difficult for me to replace a head gasket or adjust valves. If it were to be splitting the case open and replacing a crank then it would be at the limit of my wheelhouse and would require a lot more checking double checking measuring for me to do that type of thing but it's still within my abilities. I'm still using the stock carburetor all I did was I picked off the epoxy that sealed the fuel air screw I took a Dremel with a cut off wheel I cut a slat groove and that permitted me to adjust it. The stock carburetor the fuel air screw was turned all the way clockwise to the right down which with the stock settings the stock original jetting would have been the richest possible setting. I'm probably running one and a half to two turns out somewhere is right in there to get a relatively crisp response off idle when you snap the throttle. The current jetting is a 42 idle jet and a 95 main jet. And what I did was I took the Chinese knockoff carburetor apart and the needle jet was actually adjustable there was three grooves in the needle jet where is the stock needle jet has no adjustments whatsoever. So I swapped the adjustable needle jet into the stock carburetor and ultimately what I did was I moved the clip down to the lowest setting again there was only three settings the initial clip was in the middle setting. Am I moving it down it riches up the mid-range of the throttle. So if the fuel air controls the first eight to quarter of the throttle and then your idle jet then you have your needle that controls the mid-range and then your main jet begins to overlap to wide open throttle.

[luvscooters]

I initially put in the 100 main jet and it was so rich it would not rev it all I mean it was just being completely overrun with fuel and even with the airbox completely removed so the air is just going into the carburetor there was little to no difference.. now when I did that test we had 100% humidity outside in 90° weather so the conditions were terrible and if we would go to a 70° day with no humidity then maybe there would have been a chance it would have read a little bit but I still think it was way too fat. The engine should be able to run in the rain or in 50° weather with little to no changes once it's set up correctly. So I think I'm really really close at this point I took it out for a run yesterday after moving the clip on the needle jet down to enriching it and it pulled nice and smooth there was no surging anything like that there certainly was no sizing that took place. I'm just very leery at holding it wide open for any extended period the stock scooter bone bone stock except the restricted I could run it wide Open all the time and that's how I would have to use it because it's so underpowered you just grab a full fist of throttle hold it wide Open and it takes a lot of road to get the full speed and it's nice when it hits level ground in a slight downhill grade because it would fly for what it was. With the 70cc it gets to 40 very quick off idle to 5 mile an hour it's a pig and I think that has more to do with the rollers that are in it the 6 g they might need some work relative to my weight on the scooter I still need to understand how they affect acceleration I have a 1500 RPM Contra spring the yellow spring in it. So from like 0 to 5 mph the stock scooter probably would beat it but once it begins to Rev and that belt is shifting and it you know the RPMs begin to come on to the pipe range it's an enormous difference in feel again from 50 to 70 it's a big percent gain. So from 5 to 40 is very quick and going up a hill it pulls nicely you don't need to use the speed on level ground to try to get up the hill you could be coasting as you approach a hill give it gas and it will accelerate going up a hill. Where am I confusion lies is I've been around dirt bikes my whole life I've watched guys at races rebuild dirt bikes put a new piston ring kid in and breaking in for a dirt bike is running it for 4-5 minutes shutting it off starting it up running it again and then going out and beating the snot out of it. You don't have this mentality of you need 30 or 40 miles to break in and seat the rings you just run the shit out of it. There's many of engine builders on four stroke bikes race bikes that assemble it started go through one heat cycle and then it's off to the dyno for tuning and their engines hold together no issues no problems so I think there's a lot of misinformation when it comes to a scooter engine because the reality is an engine is an engine and if the rings are seated correctly and there's only way to do it you line it up to those pins and the cylinder has the hash mark honing in it the crosshatching the rings are going to seat.. so one or two heat cycles is all you should need and then run the crap out of it

[luvscooters]

The next step is to get a temperature probe whether I use a cylinder head or EGT I still have to figure it out. I know an EGT would be far more accurate the only issue is I have a MIG welder and I don't have gas and that's the only way you can weld stainless is with a gas shield. I really don't feel like paying someone 70 80 bucks to weld a bung in I mean I can drill the hole and do all of that and measure the right 5 inches or whatever the people are using from the piston alongside of the side of the pipe to get the right area to put a bung in. So I think what I may do is just get a cylinder head temperature probe and mount that just so that I know about where I stand if I hold it sustained wide open because that's the next thing I need to make sure that holding it wide Open I'm not going to lean out with the 95 jet because if the temperatures do rise substantially then what I'm going to have to do is go to 100 yet. Raising their prices to inflation and shim the needle jet the opposite direction to lean it out so I'll put the clip at the highest setting and then I'll put a couple little shim washers under that and then I'm back to square one to try to figure out the whole mid-range again and wide open.

[aeroxbud]

They do clamps so you would not need to weld a bung in the exhaust. Here is an example. www.pedparts.co.uk/product/7236/koso-egt-sensor-clamp-40-60mm

You probably need stiffer clutch springs. That would sort the game off. The NYC pipe probably needs to work at a higher RPM range to the stock pipe.