Offset intake manifold debate

Discussion in '2-Stroke Engines' started by RollingStones, May 6, 2014.

  1. RollingStones

    RollingStones Member

    I recently purchased a CNS carb but had to still with the stock carb due to the fact that the airfilter hit the frame making it impossible to accurately mount it on to the intake.

    I am am looking at offset intake manifolds online but have heard really mixed reviews about them.

    Has anyone had a bad experience purchasing them?

    If you've purchased one yourself to use with the CNS car by could you send me a link to the site you got yours from?

    Curious to hear what you guys think

  2. Fabian

    Fabian Well-Known Member

  3. AssembleThis

    AssembleThis Member

    Offset Intake

    Had to buy one myself. My first build and the power king motor fit perfectly but the throttle cable was too close to the upper post. Ordered one from boys go fast. Wow was I disappointed. It is literally a peace of scrap metal. So you could say I tossed that money in the toilet. :icon_cry: On the upside to the problem I worked as a metal fabricator and welder for quite a few years so I guess I'll fabricate one myself. Even though it involves a lot of work its better then throwing more money away. :cool:
  4. jaguar

    jaguar Well-Known Member

    The offset intake from JNMotors is good.
    You can even extend the intake even longer for a low RPM power boost. (click on my signature link to read more)
  5. dchevygod

    dchevygod Member

    What do you think guys? I already run an ADA Juice Box " boost bottle" do you think extending the the intake tract would help my low rpm torque? I can do it very easily by adding another heat spacer in between the head and juice box. In my experience with goped motors I remember that tall manifolds increase high rpm power? But without my juice box it is a dog off the line.

    Any thoughts? I'm very over geared or under powered for slow speed cruising. The hills here almost bring me to a stop, the new expansion pipe has helped a lot with high rpm power and if I get it revving it will pull most hills but slows significantly before cresting the hill.
  6. Fabian

    Fabian Well-Known Member

    A boost bottle is a complete waste of time - it's a subject that's been worked to death.

    A reed valve intake is the the best method for improving low and midrange torque, with a side benefit of significantly reducing intake noise.
    The heat isolation spacer is an absolutely essential item, but it should not be mounted in between the reed valve and the cylinder. This simply adds to crankcase volume which is exactly what you are trying to avoid.
  7. dchevygod

    dchevygod Member

    I'd let you try my g43l without the juice box and see the torque fall to almost nothing. The ADA juice box does work! Its not just a bottle tapped into the intake. Its a measured volume of space tuned for my specific engine size. Juice box

    Fabian, if you knew how much a reed would be for my motor you may not have suggested that. G43L Reed. I could almost get another engine for that, id then build a 2wd that would pull the hills ;)

    I've built reeded G43's and wasn't impressed with the loss of top end and only minor low/mid power increase.

    I'm making probably 4+ HP at 12,000 rpm with a ported, piped and upgraded 15mm carb on my g43. I think I just need to re-gear, and loose some top speed but increase my climbing ability.
  8. Fabian

    Fabian Well-Known Member

    The Chinese 2-stroke centre mount bicycle engines are a completely different thing to a G43L. The two engines cannot be compared.

    Forget even the concept of revving a Chinese 2-stroke centre mount bicycle engine to 12,000 rpm, because they have greatly reduced life expectancy after 5,000 rpm, and for good reliability it pays to keep the rpm under 4,500.
    Typically i operate the engine in to 3,500 - 3,800 rpm zone, and the reed valve intake makes a noticeable improvement to low and midrange torque with these engines; so long as the jetting is calibrated to suit the new intake system.

    I need to add that you have "ZERO" chance of making a Chinese 2-stroke engine punch out 4 horsepower and still maintain rock solid reliability; in fact, you won't even be making 2 horsepower; my engine makes even less than that, but it has strong low and midrange torque; making for a relaxed ride when sticking the bike in top gear and staying there.
  9. dchevygod

    dchevygod Member

    I need to make a flyby video of my bike at WOT and probably 45mph. This engine sings at high RPM with this small pipe on it. Intake noise is nearly nonexistent, even at speed. But its probably just the pipe drowning the noise out.
  10. Fabian

    Fabian Well-Known Member

    Like all of these things, it's horses for courses, because the engine would not last very long spinning 12,0000 rpm at WOT; going 45 mph. I concede that it will get you down to the corner shop, but if you need long distance reliability, 12,000 rpm at WOT; hour after hour after hour isn't going to allow that to happen.

    If a days riding involves 8 or 9 hours in the saddle, you need a different level of engine operation to fulfill that requirement.
  11. dchevygod

    dchevygod Member

    I only need to wot occasionally to avoid a car or when racing. In fact I've been using my bike 7-8 hours a day looking for work. Only occasionally do I need to wot to hit a hill with some speed. I cruise at +/- 30 mph

    I'm thinking you haven't had any experience with my engine. If you had you would know that wot on this motor
    Is normal and it can handle it for extended periods. The G43L is THE most reliable motor ever used on a goped, if there's oil in the gas it will last for thousands of miles. And if there's no oil it will still run for over a hundred miles, I've seen a guy that didn't know it was a 2 stroke and had been filling up at the pump. His motor was still running. And the jug didn't have a scratch?!?
    Last edited: May 18, 2014
  12. Fabian

    Fabian Well-Known Member

    I have no choice but to agree with you that i have not had any experience with the G43L, because i haven't, but i will still maintain that it's reliability would be compromised with endless (continuous) hours of use at WOT at 12,000 rpm.

    If SickBikeParts made a (centre mount) shift kit for the G43L, i would most certainly like to try it out.
  13. dchevygod

    dchevygod Member

    I agree only five years of service is to be expected when raced or run hard, instead of the 12 my bottom end has given :) with only one new cyl/piston and that's because it was ported not because the original was worn out!

    I have always wanted to do a center mount with a 460 and I don't think it would be too hard if you start with a 49cc center mount plate. I'm all about power and such. But a belt drive center mount g43 would be awesome as well I think.

    My setup really limits gearing options as is and a jackshafted 3spd hub with belt drive to the wheel sounds like a winner to me! I just wish I had the $1500 to build it right. I'd do a Motobecane 21" frame with a gebe sheave, center mount plate, and set it up as a single speed first. Then I'd adapt the 3spd hub in to a jack shaft for a shifter conversion.
  14. Fabian

    Fabian Well-Known Member

    If the G43 is such a good engine, SickBikeParts should look into engineering their shift kit to accept the G43, to give an alternative engine option for those people looking for exceptional reliability if they choose to run a 2-stroke engine.

    How does the G43 perform with a standard exhaust/muffler system?
    I am not interested in having an expansion chamber hanging out the side of the bike. I don't give a damn if it reduces engine power because i want it to be as quiet as possible.
  15. dchevygod

    dchevygod Member

    Thinking more about how SBP has there 4 stroke kit setup, I think that a G43 or a CY460 could be easily adapted to the standard 4 stroke HD shift kit. I know that a freewheel can handle the power since I use one on my LSD setup. The jackshaft just needs to be geared to the rpm range these motors run in and in the correct sprocket size. It would take some time to crunch the #'s to get the ratio right but it should be achievable.
  16. Fabian

    Fabian Well-Known Member

    Are larger capacity versions available, in the 60 or 70cc range?
  17. dchevygod

    dchevygod Member

    The g43 I currently run did gain like 5mph when I added the pipe. But the lower rpm isn't affected much at all. Actually my pipe takes a tiny bit of torque away from the low rpm. Your are lucky This motor g430rc-g43l already has a tunable 12.5mm carb. You can get a 15mm "WYK-58" and a HP filter but it's louder than stock.

    As for quiet you won't get any quieter! If you leave it all stock this motor is whisper quiet! The covered intake really helps reduce the noise and the stock exhaust is as good as it gets. My motor is race ported and with a modified stock can on it is really restricted in the high rpms but it's quiet as a mouse fart!

    Since your going shifter it shouldn't matter much at all that your high rpm will be about 9500 loaded. I'd definitely still install the juice box for a proven low RPM torque/HP increase. This motor will last the test of time if left all stock, I just don't think that way though! MORE POWER!!!!
  18. dchevygod

    dchevygod Member

    There is a Zenoah g62 but its not affordable "over $1200 in the state we could use it". And the power that the stock G43 makes "reliably" can't be beat.
  19. Fabian

    Fabian Well-Known Member

    Only from an aesthetics point of view, i will say that the conventional Chinese 2-stroke centre mount engine looks like a proper engine, whereas the G43 looks like a whipper snipper/weed wacker power head.

    Can you get billet cylinder heads for the G43 with significantly greater cooling surface area?
    I spend a lot of time off-road negotiating goat tracks at 3 - 5 mph; hauling a lot of weight up steep gradients. The engine would be under a lot of load with next to no airflow moving over the cooling fins?
  20. dchevygod

    dchevygod Member

    Headkits used to be available, you may get lucky and find one used. Because this is an old motor that has been replaced by the gp460, that's way too loud "even stock". The g43 has a cooling fan on the flywheel! I don't get your concerns about slow speed? I get slowed to less than 5 mph all the time on the hills here, I've only experienced power loss once from heating it too much one time and that was with the stock exhaust can heating the jug, it runs way cooler with the pipe installed. A poopoo pipe will do the same thing and be even more quiet and restricted than the stock can. The fan shroud can be trimmed so it looks more appealing. Or removed if you locate a head kit.