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chaz e z
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| Sun Jun 29, 2008 4:34 pm I know rollers again... |
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| There are loads of topics about rollers but I'm still not sure which ones I should buy. I really need to improve my acceleration and from what iv read rollers improve it. Which ones should I get to improve? |
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Fox
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| Sun Jun 29, 2008 7:01 pm |
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It says RX 50 on it so for a 50cc you should go with some 16mmX13mm 4.4 gram
Try these:
http://beedspeed.com/variator-roller-weights-16mmx13mm-44g-malossi-p-3144.html?cPath=74_227_248&osCsid=9ba333347d5be0cb59124ed11455c84d |
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chaz e z
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| Sun Jun 29, 2008 8:31 pm |
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| thanks, I'll look for rollers like this when I go 2 shop tomorrow |
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DaveS
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| Sun Jun 29, 2008 8:36 pm Re: I know rollers again... |
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chaz e z wrote: There are loads of topics about rollers but I'm still not sure which ones I should buy. I really need to improve my acceleration and from what iv read rollers improve it. Which ones should I get to improve?
If you do not have a rev limiter in your CDI, there is one thing you need to watch out for with the light rollers. I put some Dr. Pulley 4.5 gram rollers in my YY50QT-6 with a 139QMB engine yesterday and took it out for a trial run in the hills around here. The light 4.5 gram rollers did improve acceleration and hill climbing very noticeably, but they over reved the engine a lot when accelerating down hill or even on the flats. I saw over 10,000 RPM on my TinyTach on some trip segments, and that seems a bit much to me? However, it did let me know I do not have a rev limiter in my CDI. As soon as I got back I put the old 7.5 gram rollers back in because I do not want to blow my engine just yet. I think that I will try some rollers with weights somewhere between those two extremes next. FWIW, the 7.5 gram rollers never seem to let the engine get over about 7000 RPM in any condition, and that is well below the peak horsepower RPM. |
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chaz e z
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| Sun Jun 29, 2008 8:44 pm |
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| ohh right, I dont have a rev limiter so what would you think is the ideal rev limit I should get and how much weight on the rollers. I was thinking I should test out these rollers and if it over revs buy heavier ones. I do not yet know the weight of the ones I have at the moment because I am sorting it out tomorrow and getting a new drivebelt too :) |
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Fox
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| Sun Jun 29, 2008 8:54 pm |
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| I wouldn't put too much faith in that Chinese Tach. :roll: |
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chaz e z
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| Sun Jun 29, 2008 8:59 pm |
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oh so I should be ok then. But I am now worried that I will lose some mph from my top speed reading from another topic. Do you think I will? It is de-restricted
thanks |
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DaveS
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| Sun Jun 29, 2008 9:03 pm |
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chaz e z wrote: ohh right, I dont have a rev limiter so what would you think is the ideal rev limit I should get and how much weight on the rollers. I would like to know the ACTUAL red line RPM myself!!! I thought that I had read on this forum somewhere that some CDI units limit the maximum RPM to about 8000, which seems reasonable since the peak horsepower RPM for 139QMB engines is usually stated in the specs that I have read as about 7500 RPM. As far as I know, the only way that you are going to be able to determine the ideal roller weights for your machine and your driving conditions is by experimenting. That is what I am doing. That is also why I got an accurate tachometer to use while I am experimenting.
chaz e z wrote:
I was thinking I should test out these rollers and if it over revs buy heavier ones. I do not yet know the weight of the ones I have at the moment because I am sorting it out tomorrow and getting a new drivebelt too :)
I did not know the weight of my rollers when I first started either. I weighed them when I took them out to put the 4.5 gram rollers in. Now I know what runs *my* engine too slow and what runs it too fast, so I can now search between them for the ideal weights for *my* situation. |
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chaz e z
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| Sun Jun 29, 2008 9:15 pm |
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| ok, I need to try and get it right first time because I don't have much money to use at the moment. I just need some decent ones to improve the acceleration because it stinks at the moment. |
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DaveS
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| Sun Jun 29, 2008 9:17 pm |
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Fox wrote: I wouldn't put too much faith in that Chinese Tach. :roll:
After reading articles in this forum for a while I would not put ANY faith in a Chinese analog tachometer that comes built in. :shock:
Being a retired digital electronics engineer, I tend to trust digital electronic devices much more. That is why I am doing my roller experimentation using a TinyTach. I think the TinyTach is accurate to plus or minus 1 RPM, and there are probably no analog dial indicating tachometers that can come even close to that. The TinyTach is just stuck on to my panel with double stick tape because I only intend to leave it there for roller experimentation. Since I don't expect to always have the tach, I want to find a roller setup that will always load limit the engine to a safe RPM value. My current goal is to find roller weights that will be fully extended at 8000 RPM, which is about 1000 RPM higher than my stock rollers load limit the engine to now. |
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DaveS
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| Sun Jun 29, 2008 9:25 pm |
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chaz e z wrote: ok, I need to try and get it right first time because I don't have much money to use at the moment. I just need some decent ones to improve the acceleration because it stinks at the moment.
IMHO, 50cc acceleration is ALWAYS going to stink, but it can obviously be better than the stock roller weights will give you. A lot of people here seem to reccomend roller weights in the 4.5 gram range for good acceleration, and I have not read of a blown engine due to that on here yet. I just wanted to make you aware of what I found out with my own experiments yesterday. I may be way to worried about seeing my RPMs get up around 10,000 and probably would have been really happy with them if I did not check my results with an accurate tachometer. Maybe 10,000 RPM is OK???????? :? |
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chaz e z
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| Sun Jun 29, 2008 9:39 pm |
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| does the engine sound ok at 10,000? I thought I would sound like its about to blow up if it went up to that, but I arent to sure myself to be honest |
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DaveS
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| Sun Jun 29, 2008 9:46 pm |
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chaz e z wrote: hmm does the engine sound ok at 10,000? I thought I would sound like its about to blow up if it went up to that
Nope, it sounds perfectly fine at that speed. If the valves had started to float at that speed it would NOT have sounded fine, so I know that the valve float limit on *my* particular engine at this point in time is above 10,000 RPM. Back in my teenage drag racing days I saw what valve float does to V8 engines, and it is not pretty. That is part of the reason I am being cautious about how I select my roller weights. The problem is, I really do not know what the maximum safe RPM is for the 139QMB engine!!!!! :? |
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chaz e z
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| Sun Jun 29, 2008 9:53 pm |
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| well I best be careful to then because I am in the teenage drag racing days still. Have to tried looking on google for any pointers? I looked for your moped and it said MAX RPM:8500 haha but I'm guessing thats with all the factory parts installed |
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DaveS
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| Sun Jun 29, 2008 10:11 pm |
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chaz e z wrote: well I best be careful to then because I am in the teenage drag racing days still. Have to tried looking on google for any pointers? I looked for your moped and it said MAX RPM:8500 haha but I'm guessing thats with all the factory parts installed
I have looked, but I have not found anything listing the "maximum safe RPM" and the max torque and and max horsepower RPM values seem to be all over the place. The highest max horsepower RPM value that I have found is at 8000 RPM, and since power actually decreases above the max horsepower RPM value, that 8000 RPM number is what I am trying to get with the roller weights that I finally select. In my case it looks like it *may* be around 5.8 grams, but I have not tested that yet.
Can't post anymore tonight, since I need some sleep. I hope that you find whatever works best for you!!!! |
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