improving Velocity!!?!!!
- Thread starter Triplecrown421
- Start date
i took the bike out yesterday!! went for a 2 or 3 hour tour to some pits to try it out. The bike didnt lose any power at top end at all, there is deffinitly no lose in power through the full torque curve. it seems that this is not restricting the airflow at all.
Now for the assDyno throttle response did seem improved altho it didnt seem much. it did feel like it improved the torque curve abit aswell. This is all just from what i think off of the first try. i should get Best to try it and see what he thinks. the good thing about all this is it didnt affect hp in a bad way. Ill have to get some more seat time on it.
abit odd but the bike ran alittle lean aswell, odd cuz i leak tested it before and after the ride and it passed. Im running a 270 main and have been for more then a year. so im gonna do a chop and see where i gotta go but it just seemed weird cuz i havnt had this problem with thiis jet. ill be cleaning the carb before the next run aswell.
Now for the assDyno throttle response did seem improved altho it didnt seem much. it did feel like it improved the torque curve abit aswell. This is all just from what i think off of the first try. i should get Best to try it and see what he thinks. the good thing about all this is it didnt affect hp in a bad way. Ill have to get some more seat time on it.
abit odd but the bike ran alittle lean aswell, odd cuz i leak tested it before and after the ride and it passed. Im running a 270 main and have been for more then a year. so im gonna do a chop and see where i gotta go but it just seemed weird cuz i havnt had this problem with thiis jet. ill be cleaning the carb before the next run aswell.
Nice ! glad to hear it didn't affect the top end any , also weird about the lean condition , maybe go for another ride with new plug then plug chop it and see where your at , after you clean the carb that is , just a suggestion , Glad to see its not Loosing anything as well and like the fact its changing the torque curve some !!
I cleaned out the carb out and noticed there was some bits of dirt in the bowl, gotta line filter on it now, I think that may have been my leaning issue.
i had plug choped the bike before the port stuff work and it worked best with a 270 todays plugchop with the 270 showed too rich. i installed a 250 main and put the needle on middle setting.
MUCHH BETTER!! this thing works i kinda noticed the port stuffing improved the mid range torque and response but did help the topend aswell.
This really dos seem like a good spot to improve minor restrictions. i can bet this may help with opening ports up aswell, fill in the oversized areas and port out whats left to try and match things up better
i had plug choped the bike before the port stuff work and it worked best with a 270 todays plugchop with the 270 showed too rich. i installed a 250 main and put the needle on middle setting.
MUCHH BETTER!! this thing works i kinda noticed the port stuffing improved the mid range torque and response but did help the topend aswell.
This really dos seem like a good spot to improve minor restrictions. i can bet this may help with opening ports up aswell, fill in the oversized areas and port out whats left to try and match things up better
sux about the dirty bowl , glad to hear it improved top end as well this time , whats the plan with it now , changing it again ?
with the lowered intake vol and at its best now i may try some boost bottle theory's maybee. i did just get a 15 tooth front sprocket from ebay which i would like to try, i am currently running a 14. it may help show some of the performance better
nice a 15 , never ran that big , be careful with a 15 , make sure you have good clearance in there for it !
ya i hurd you have to trim some off the the side cover to make it fit, it should be pretty sweet. with my 18 tires it should get a max speed of about 90 kph
Ok, I finally got to ride Triplecrown's beast last night.
First off, let's clear up some details:
The intake windows into the cylinder were smoothed on all edges and opened up top and out sides slightly, previously.
Other than smoothing out the cylinder liner/casting mismatch, the bridge was not narrowed or reshaped, left square, then streamlined taller.
So, the intake windows are slightly larger, 1mm up and about 0.5mm out.
The epoxy and aluminum plate was to take up volume around the reed valve and in the port to keep cross sectional area as consistent as possible.
It is not a restriction. Still running the 26mm stock carb. Exhaust port raised 1mm, cylinder low 0.030", modified head, 15 tooth sprocket now.
Bike starts good and idles steady, good power as you accelerate from idle. No bog anywhere.
Low rpm has good power, more than than stock, hauls the 15 tooth front sprocket in sand.
The powerband seems to kick in much lower than it ever did before, sort of before the mid-range and certainly lower than the DT200 with or without the powervalve.
Here I have to explain that the tires, air pressure and extra swingarm length on Triplecrown's bike make for NO traction for the extra power this quad has now.
The power from the low mid-range makes a quick jump into the powerband and then rises quickly.
The surprising thing is that the powerband and rpm range has extended greatly.
Pipe no longer limits max rpm so it is very easy to "over-rev" the engine, especially with little traction.
On hillclimbs and acceleration you have to constantly modulate the throttle to avoid spinning out.
More work on traction needed.
The engine is much more lively in the upper rpm range and revs higher than before the intake filling.
This is a surprise to me, I didn't think the intake had that much effect here. I thought pipe and exhaust were the big determinates for rpm range and powerband. Neil briefly tried a PWK 39 carb the day before for no ready gain, so he switched back to the 26mm. Plug chops indicated the engine was rich, so he dropped his jet from 270 to 250. I questioned it, so he double checked before we rode it hard. Ride it hard we did. No overheating in this hot weather, no detonation, no signs of the 250 being lean. We actually took another 0.020" off the head, closing the squish to 0.050 in preparation for raising the cylinder and to test detonation limits. This firmed up the power throughout the range, even top rpm, which goes against what I have seen on my KTMs.
It is my theory that the tighter intake is keeping the fuel in suspension better.
That would mean whatever fuel you delivered at the carb is getting to the combustion chamber at all speeds.
A heavily ported high volume intake would cause a drop in velocity, fuel would drop out and settle along the floor and into the bottom of the crankcase, building up at idle and low speeds. Full throttle would result in an initial lean condition, then a splash of liquid fuel and oil (big initial smoke on WOT) and then a big part of the charge dribbling down the floor of the reed case. The liquid fuel does not burn well. You would have to have richer jets to make up for this. My thought is the tight intake is "shooting" the air/fuel charge past the reed case dead zone.
The next direction was to raise the cylinder 0.030" with a basegasket.
This should raise rpm more and take from the mid-range slightly.
I don't know if we want to go that direction, but it is an easy test.
Where now? Any thoughts guys?
First off, let's clear up some details:
The intake windows into the cylinder were smoothed on all edges and opened up top and out sides slightly, previously.
Other than smoothing out the cylinder liner/casting mismatch, the bridge was not narrowed or reshaped, left square, then streamlined taller.
So, the intake windows are slightly larger, 1mm up and about 0.5mm out.
The epoxy and aluminum plate was to take up volume around the reed valve and in the port to keep cross sectional area as consistent as possible.
It is not a restriction. Still running the 26mm stock carb. Exhaust port raised 1mm, cylinder low 0.030", modified head, 15 tooth sprocket now.
Bike starts good and idles steady, good power as you accelerate from idle. No bog anywhere.
Low rpm has good power, more than than stock, hauls the 15 tooth front sprocket in sand.
The powerband seems to kick in much lower than it ever did before, sort of before the mid-range and certainly lower than the DT200 with or without the powervalve.
Here I have to explain that the tires, air pressure and extra swingarm length on Triplecrown's bike make for NO traction for the extra power this quad has now.
The power from the low mid-range makes a quick jump into the powerband and then rises quickly.
The surprising thing is that the powerband and rpm range has extended greatly.
Pipe no longer limits max rpm so it is very easy to "over-rev" the engine, especially with little traction.
On hillclimbs and acceleration you have to constantly modulate the throttle to avoid spinning out.
More work on traction needed.
The engine is much more lively in the upper rpm range and revs higher than before the intake filling.
This is a surprise to me, I didn't think the intake had that much effect here. I thought pipe and exhaust were the big determinates for rpm range and powerband. Neil briefly tried a PWK 39 carb the day before for no ready gain, so he switched back to the 26mm. Plug chops indicated the engine was rich, so he dropped his jet from 270 to 250. I questioned it, so he double checked before we rode it hard. Ride it hard we did. No overheating in this hot weather, no detonation, no signs of the 250 being lean. We actually took another 0.020" off the head, closing the squish to 0.050 in preparation for raising the cylinder and to test detonation limits. This firmed up the power throughout the range, even top rpm, which goes against what I have seen on my KTMs.
It is my theory that the tighter intake is keeping the fuel in suspension better.
That would mean whatever fuel you delivered at the carb is getting to the combustion chamber at all speeds.
A heavily ported high volume intake would cause a drop in velocity, fuel would drop out and settle along the floor and into the bottom of the crankcase, building up at idle and low speeds. Full throttle would result in an initial lean condition, then a splash of liquid fuel and oil (big initial smoke on WOT) and then a big part of the charge dribbling down the floor of the reed case. The liquid fuel does not burn well. You would have to have richer jets to make up for this. My thought is the tight intake is "shooting" the air/fuel charge past the reed case dead zone.
The next direction was to raise the cylinder 0.030" with a basegasket.
This should raise rpm more and take from the mid-range slightly.
I don't know if we want to go that direction, but it is an easy test.
Where now? Any thoughts guys?
This mod has worked very well, boosted power and throttle response throughout the rpm range, lowered powerband cut in and raised top rpm, totally broadening the powerband. I had used Boyeson and V-Force reeds on the KTMs and noticed slight improvements, which of course I always associated with the pedal design.
Triplecrown came up with the idea; "Do you suppose they work better because they take up more volume in the reedbox?"
I think he may be on to something there...
Boyeson pictured:
Triplecrown came up with the idea; "Do you suppose they work better because they take up more volume in the reedbox?"
I think he may be on to something there...
Boyeson pictured:
So you are thinking on the boysens, there design of a smaller opening creates better velocity? I believe the petal part is the same as a stock cage. Now the VF-3 cage takes up more space inside the intake on the motor than the boysens do I would think as the petal surface is larger.
Yes, even the Boyeson has more metal taking up volume in the reedbox than the stock KTM reeds. The petals are different on the Boyesen and flex differently. Actual window opening on the Boyesen is only slightly larger. The Boyesen seems to favour high rpm without affecting the low rpm performance of the stock reeds.
The VF3 is a LOT of plastic stuffed in the reed box. Yes, lots of petal area, but I gotta wonder if Neil is on to something about the volume they take up. Petal area should only be a restriction to max flow, max rpm power, and yet both Boyesen and VF3 offer slight gains throughout the powerband, but the VF3 tended to favour low rpm better.
The gain we got from stuffing the box was better than I got switching to the Boyesen or VF3 on the KTM. I wonder if you were to combine the two? Although the size of both might limit the amount of epoxy you can get in the reedbox.
Something to think about...
Very interesting!!!! I would like to see the results with a Mossbarger Powergroove reed valve or Pyranid reed valve!!! >>> Duncan Racing International: Pyramid Reed Valve Yamaha Blaster >>> Mossbarger Racing Products, LLC
so instead of filling the entire intake with epoxy could a mold of some sort be made to bolt on with a reed cage? that would just be like a big funle between the reed cage and intake ports. that way it could be compatible with port work with very slight adjustment. if there were a way to fill the intake port with something, with the reed cage attached then cut away what wasn't needed and port the insided of that to the cage. (not sure if i'm making any since here)
i was also thinking if you took a reed cage and tapeover the reed stops to create a void for the reeds to open it might speed up the trial and error portion. you could just bolt the reed cage on and poor the intake full with appoxy. well at least the outside reed portion. i dont' know just some of my thoughts.
i was also thinking if you took a reed cage and tapeover the reed stops to create a void for the reeds to open it might speed up the trial and error portion. you could just bolt the reed cage on and poor the intake full with appoxy. well at least the outside reed portion. i dont' know just some of my thoughts.
Pretty darned good thoughts I'd think Scott.
I have used soft silicone rubber to get a mould of ports and used it to create other ports by lathering up the port with epoxy and sticking the silicone moulding in as a former. Leaves bubbles and voids that need repair but works well enough. I especially like the idea of taping up the reedcage to get the perfect pedal stops cast into the epoxy in the reedbox.
Here are some pictures to ponder:
Stock Ktm reedboxes. notice the filler block removed from one?
Run without it it is similar to a Blaster's and power is reduced across the board.
The horizontal divider is removable as well, and seems to improve mid range.
Here you can clearly see the different size stuffer blocks, even the horizontal wing varies in thickness.
These go BEFORE the reeds and most KTMs run the same 38/39mm carb, 125-380cc.
Not where you would usually put stuffing on a 2 stroke but have quite and effect on improving power.
Even the Boyesen has the same stuffed interior:
On a related thought, I glued horizontal dividers into the carbs and ports of my KZ1000 Kawi. So effectively it reduces the port volume under 1/2 throttle in half. The bike runs rich on unchanged jets, and has greatly increased torque under 5000rpm. Power over 6000rpm is not good and it breaks down, which may be because the plates nearly touch the valve and are not bet to follow the port, ie they may mess up the flow over 6000rpm. So, essentially I gave my screaming Kawi the powerband of a Harley, fat and low. Not totally an improvement but great around town. Fuel mileage on slower 50mph/80kph roads is up 15%, on 100kph/65mph highways up 10%.
Next step is to shorten the port dividers to before the valve curve.
This applies to Blasters where you can do it to the carb and reedbox, like the KTM reedboxes above. Wanna try it?
bike is working awesome had it out yesterday for almost 5 hours and it was HOT OUT!!! no jb has let go and im not worried any will. Im running a 15/40 on 22" tires, motor has no problem clicking through the gears and maxin at almost 100kph, i think my clutch is finally gettng abit weak.
If one is trying to squeeze every last bit of performance out of there blaster this is something i recommend. I dont think there is anywhere else in the motor that is worth filling portwise.
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