|Topic Review (Newest First)|
|4-26-2019 3:42 PM|
The whole problem is the title of this thread is a oxymoron. the solution is not a solution just different, and not as good.
So the solution solves nothing.
|4-26-2019 3:00 PM|
|yorkie||yeah that's a good plan never do modifications to running bike you use every day. unless you have to.|
|4-26-2019 1:36 PM|
Originally Posted by yorkie View Post
I actually have ulterior motives. People use these powerplants in microsprints too, and if I can find a good combo, my buddies will benefit from that knowledge and it will be a tidier system. Plus I'll have the knowledge for a clean custom framed streetfighter/tracker build I'm planning.
My daily rider runs like a champ, stock, and I have no plans to do anything but the FOG mod -- K&N filter came in yesterday.
|4-25-2019 6:07 PM|
with all due respect there's a world of difference between a YZ125 and a EX. I am sure you find that out when you start. let us know how it goes.
VM28's are a better choice than a 34mm tilly due to the CFM flow rate. you never know you may just hit the sweet spot quite quickly and prove everybody who has gone this route wrong.
you know it's a bit like the scene from Karate Kid "the one where they are catching flies above a candle" someone has be lucky.
|4-25-2019 4:18 PM|
FWIW, old Harley's used Tilly's..... But I'm not exactly happy with Harley's or how they run, so.... Anyhow, in the karting world, we've put tillys on YZ-125's with no issue, though they spend most of their lives at mid- to high- RPM.
When I find a project EX and streetfighter it with a single pipe, I hope to make some custom manifolds and use VM28's...
|4-25-2019 4:55 AM|
CVK carbs depend on vacuum in order to work. and as you have no direct control of the slide openings they are in fact semi automatic in operation also due to the restrictive nature of system they tend to be bigger than is actually required.
when you change the carbs to fully manual slide operation a whole new criteria appears including the size of the unit as well as the flow rates to get the mixtures correct at all slide positions. I think the OP is underestimating the complexity of trying to fit same size units of a different design onto the EX. it may improve the drivability and flexibility of the power curve. but at great cost in time and effort.
guess how I know.
|4-24-2019 6:00 PM|
Originally Posted by fog View Post
Yes, the CV stands for Constant Velocity, to achieve optimum driveability while allowing maximum flow. IMO, a properly clean and adjusted CV carburetor is the next best thing to fuel injection.
I'd still be curious to see this experiment though.
|4-24-2019 1:01 PM|
If your throttle response is slow or abrupt, you are certainly too rich down low.look to your jetting you can't get better off the stop responds than a CV carb.
your spitting off the windward rail
|4-24-2019 11:39 AM|
If you're looking for mid range "response", you're NOT going to find it with a Tillotson carb.
Actually the best carb for mid range would be a CV carb, like the stock one.
|4-24-2019 9:55 AM|
The primary benefit, to my mind, would be better throttle response.... I had also considered looking into a pumper carb setup from a 250f MX bike, with custom manifolds for each side... I don't want more power, I want better response. Typically, a SMALLER carb results in more throat velocity, and better throttle response...
My exercise is more theoretical... I don't plan to modify mine from stock, beyond the FOG mod and occasionally re-syncing.
|4-22-2019 8:57 PM|
|K-woppa||I haven't heard of any great success using those on a four stroke street bike. It would be an interesting experiment though.|
|4-22-2019 8:37 PM|
No it is not a better way to carburetor this engine. Yes it is tuned (mechanical designed) to the max, actually past the max structurally . The prevalence of blown head gaskets bears witness to this fact. We donít hear much about the crankshaft.
The engine is cut right in half by the cam drive in the middle. The two halva are held together only bi thin webs of aluminum. This allows,nay causes the engine to twist itself into a pretzel.
Also the crank needed a extra bearing and is too long a wipes terrabiblly then the hung the lump of a alternator on the end.
Is short it is not a good candidate for modification .
|4-22-2019 8:01 PM|
What is it you're trying to achieve?
Why not run VMs or PWs and use throttle plate signal like normal people?
|4-22-2019 7:24 PM|
Originally Posted by Kennylxix View Post
|4-22-2019 7:02 PM|
|Kennylxix||Would there really be much to gain? I've heard more than a few times that these engines are tuned pretty well.|
|4-22-2019 5:37 PM|
If your going to do all that work , do it to suit a 35mm choke Webber carb ,like a 40 DCOE and have all you need .
|4-22-2019 4:44 PM|
This model has a boot connection type:
|4-22-2019 4:40 PM|
Coming from the high performance karting world, if I was going to try to adapt a set of pods to an EX, I'd start with a kart carb, and have a custom machined manifold. Alternatively, a rubber boot mount would work too...
I'd use a pulse-driven Tillotson , pulse driven off the crankcase. 34mm bore carbs.
I'd machine a manifold that had studs to mount the carb, and rotate the carbys to allow for easier needle access (ie. 30*)
Drive the diaphragms off crankcase pulse. No floats = less hassle, and adjustable jets simplifies tuning.
You'd have to work out how to sync the throttles. I'd use a single cable pull going to a "Y" rod that had r/c car turnbuckles for tuning. Sync as usual via vacuum.
The pods are simple, after that.
For the manifolds, it would be possible to 3D print a core, make an investment casting, and use that.
For a skilled homebrew guy, or a garage CNC'er, not too big a deal. Shoot, I may have to do it...
But for now, I'm happy doing the FOG mod.