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Thread: deciding which cylinder exhaust and carb to get

  1. #1
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    deciding which cylinder exhaust and carb to get

    hi looking for some advice, i know theres loads of threads on this but im looking for a specific setup.im rebuilding the engine on my 1999 project next week, full strip down with every bearing replaced. im looking for a reliable set up, not too fussed about top end speed as will only be for weekend rides when warm in the uk so will not be used very much.

    will be keeping it with a standard crank so should i just stick with a standard 50cc top end and just put a bigger carb and exhaust on?

    or if i decide to go the bbk route i have seen top performance kits have good reviews , what carb, exhaust would suit this kit?

    i have seen stickyparts be mentioned on here a lot but think these kits are now obsolete

    im looking for a carb with manual choke as the 1999 doesn't have the lever on the handlebars

    any advice would be greatly appreciated cheers

  2. #2
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    On AM6 the stock crank is a big disadvantage. It will surely break on the ignition side with a better kit.

    I would recommend the following setup: Polini CP 19mm, Doppler ER1, Airsal 70-80, polini clutch plates And a Yasuni R3 exhaust. This is relativly a cheap for its own price/value. A lot of us in Hungary using this setup.

    But you need to decide where to go, high rpm powrrband with less torque or lower powerband with more torque. Thats what you need to decide.

  3. #3
    apriliaforum expert Spudgun60's Avatar
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    As you say. Stickyparts has gone the way of the Dodo. I used their 7 port and 5 port cylinders when I had my Aprilia. There is some good news though. The 7 port cylinder is available from somebody else.

    https://www.ebay.co.uk/itm/Lextek-70...y8k:rk:10:pf:0

    I can't vouch for the quality. This is the 70cc version of the stock cylinder that was used from 1998 backwards (It does require this cylinder head).

    https://www.ebay.co.uk/itm/50cc-Cyli...item59184a7f9c

    I used the Stickyparts version for over a year with a stock crank with no problems. I also had an Arrow 'Street' exhaust and a 19mm Dellorto carb.

    The bike maxed out at 65mph and had a 13T gearbox sprocket.
    Gone, but not forgotten. 1999 RS50.


  4. #4
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    Thanks for the replies, that yasuni r3 exhaust is quite expensive, it’s Ł100 more than the arrow street . Think I’ll go with spud guns suggestion . Not sure about the quality of this eBay stuff tho . Would the arrow set up along with 19mm carb work well with a 70cc top performance kit? I’ve not heard good stuff about the airasal kits so might swerve them

    Also what dellorto 19mm carb comes with a manula choke? Or is it just a case of fitting a manual choke conversion kit

    cheers

  5. #5
    apriliaforum expert Spudgun60's Avatar
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    The Stickyparts 5 port BBK I had was a clone of the Top Performance black BBK. That worked well with the Arrow 'Race' exhaust (It was crap with the 'Street'). I did use this setup with a 19mm carb for a short while. Then I fitted a 21mm carb. If you're not all that worried about performance, then the 19mm carb is fine.

    I had a cable choke on my carb. I changed the left hand handlebar cluster for one from an RS125. I did have to swop out the internals (Easy job), but it worked just fine.

    Oh. While I'm here. The headlight unit from an RS125 is way better than the RS50 lamp!
    Gone, but not forgotten. 1999 RS50.


  6. #6
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    Like kaldis said,carb from polini,its next level shit...

  7. #7
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    If you want performance then go for the Airsal kit. They will propably last longer than that ebay stuff. Used a lot of Airsals never had any problems. A nice 20.000kms with one piston which is crazy. Airsal is mostly perform better/last longer than some Top performances.

    For the carb go for the Polini. Way better performance.

    About the exhaust. Again if you want performance go for the Yasuni R3, way better for a 70-80cc kit. Arrow is made originally for 50cc. It will restrict. Just look at it diameters.

  8. #8
    apriliaforum expert Spudgun60's Avatar
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    Quote Originally Posted by Kaldis12 View Post
    About the exhaust. Again if you want performance go for the Yasuni R3, way better for a 70-80cc kit. Arrow is made originally for 50cc. It will restrict. Just look at it diameters.
    I can't really agree with you there. I've used both the 'Street' and the 'Race' versions of the Arrow exhausts. Both on 70cc cylinders. I agree that both exhausts works on 50cc cylinders. However. Both work equally well on 70cc BBK's. To say that these exhausts are restrictive for 70cc kits (in my opinion) is speculative.
    Gone, but not forgotten. 1999 RS50.


  9. #9
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    Yes it definetly is. It very muchly depends on the setup. Most likely you can achieve way more power with lets say the Yasuni r3 than the Arrow. Arrow has the diameters just in the middle. Its kinda good for a weaker 70cc but it works very well with a 50cc.

    But one thing is that with an other exhaust you can achieve more power. Just need to look at the power band and decide what you want. Arrow has a lower powerband as the Yasuni has a higher powerband. Choose what you want. But firstly decide what cylinder do you want.

  10. #10
    apriliaforum expert Spudgun60's Avatar
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    Ah. You've just hit the nail on the head. That is: What you you want?

    I used the Arrow 'Street' Exhaust with the Stickyparts 7 port cylinder. The 'Street' exhaust was hopeless with the Stickyparts 5 port cylinder. Conversly. The Arrow 5 cylinder port didn't like the Arrow 'Street' exhaust', but was excellent with the Arrow 'Race' exhaust.

    The reducto being: A 2-stroke engine is a total system. All parts have to match and work together, in order to be effective.

    If you have a cylinder that gives its maximum power at a lower rpm. Then it would be counter productive to fit an exhaust where it is resonant at a higher rpm (makes sense). As you say: Decide what cylinder you want and then buy an exhaust to match it.
    Gone, but not forgotten. 1999 RS50.


  11. #11
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    Thats all about it. For lets say a 70cc cast iron the Arrow race would be propably perfect, but as on the other side. For lets say a Tpr 70 Aluminium the Arrow would be too small and would need a bigger exhaust.

    I mean not just the RPM what matters, the displacement matters too, but not that much like the rpm. An arrow exhaust could even handle an 80cc kit. Rpm would be an issue tough, just like as the overheating. I would say that the arrow maximum line would be at a 70cc cast iron kit.

  12. #12
    apriliaforum expert ToraTora's Avatar
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    Cool

    I know it takes a lot of effort, but it really is worth while to look through the threads. The Airsal is a decent product for the money. One of my favorite kits was an Airsal that I did some modding on, but I had such a customer service nightmare with them that lasted over two years, because they put the wrong parts in the box, that I can no longer recommend them.

    The kit that I like the most for the kinds of activities you are describing is the Italkit Giladoni. They made some of the nicest top ends you can buy in an affordable kit. The quality is well beyond what I've seen from Top, Airsal, etc. They wore originally a 48mm bore, but they recently introduced a 50mm bore too. I've used them on AM6 and Derbi Euro2 engines. Great kits, work well, and since the are made well they can last a long time.

    Personally I do not like the cast iron cylinders. The aluminum cylinders cool better, and you don't have the warmup disparity if both the cylinder and piston are the same material. This means you are less likely to get a cold seize.

    I also don't like running two rings because it creates twice the friction, and it only provides ~5% more compression, which you can make up for with the design of the cylinder. With much larger bores say like for a 250CC engine sure you need the second ring to keep the piston square, but you don't need it in these small bore engine. Also, the single ring kits tend to come with much better pistons, and that alone is reason enough to get a single ring kit. At the higher RPMs that these little engines run the friction from the second ring is a much bigger deal than with the bigger bores that run at lower RPMs.

    It's a good idea to decide on which kit you want to go with, and then the other items can be determined. Any other method is kind of like putting the cart before the horse.

    The one thing that you really should consider though is getting a decent crank for the engine. The AM6's crank is one of its known weaknesses. By upgrading the crank you'll have a much nicer engine. Lots of people like the top of the line Doppler crank, but there are other good ones out there too. The Doppler is just a good crank for a reasonable amount of money, with many happy customers. I'm running one of them in a Derbi Euro2 engine, and it has been a solid dependable part of the build.

    If you did want to get a performance setup then I would look at the TRT 2Fast 70cc kit, the Metrakit Prorace, and the nicer Bidalot kit. All of those are great. I have a bunch of Metrakit stuff, and they have made very nice kits. I recently got a TRT2Fast 100cc system, and it is just amazing. Nicest kit I've bought for one of these bikes yet—yes it was expensive, but so worth it.

    I've bought a lot of different kits, and I've done a lot of experimenting—which means that you don't have to take the risks. You can read through my threads to see what works, and what doesn't. Saves you from a lot of headaches that's for sure!

  13. #13
    apriliaforum expert ToraTora's Avatar
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    Quote Originally Posted by Spudgun60 View Post
    I can't really agree with you there. I've used both the 'Street' and the 'Race' versions of the Arrow exhausts. Both on 70cc cylinders. I agree that both exhausts works on 50cc cylinders. However. Both work equally well on 70cc BBK's. To say that these exhausts are restrictive for 70cc kits (in my opinion) is speculative.
    Depends on the carb. The Arrow can handle up to a 21mm carb, but if you go to a 24mm carb the Arrow will not allow you to get the full performance from the larger carb. In that way it does restrict, and it is not speculative.

  14. #14
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    Also Tora, Italkit introduced the 52mm bore a few years ago.
    And as for the Arrow exhaust, I wouldnt put it on with a 70cc 21mm carb kit. Overheating would be an issue there. Maximum would be the 19mm in my opinion. Anyway I think just keep the Arrow exhaust for the 50cc kits.

  15. #15
    apriliaforum expert Spudgun60's Avatar
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    This talk with over heating and Arrow exhausts piqued my interest. So much so, that I went back and looked at the videos I made (I had a camera strapped to the tank). Here's what I found.

    7 port cylinder.
    Arrow 'Street' Exhaust
    19mm carb
    By and large. The needle sat just under the 1/2 way mark. The only time it went over, was when I had to go up prolonged inclines. Once the road flattened out. The needle went back to just under the 1/2 way mark again.

    5 port cylinder.
    Arrow 'Race' exhaust.
    21mm carb.
    The needle sat at the 1/4 mark. Even going up the same prolonged incline. The needle never went over the 1/2 way mark.

    Just one small note: In the video where the needle went over the 1/2 mark. I had taken off the screen as it was crazed (The camera couldn't really see where the bike was going). I think the links to the videos are in another thread. I could Post up some screen grabs though.
    Gone, but not forgotten. 1999 RS50.


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