| Author | Message | ||
     Tsunamix |
I'll stop bothering EZ all the time and try asking some of you guys for your thoughts. So recently I bored out the head a little bit, added an intake and changed the jets out to 45/170. Of course I adjusted the idle screw, 2 1/2 turns as I found out from before. I then learned I needed to shim the needle(?) I used this 4mm spacer I got from OSH that fit. So now as I throttle it gets a real good low-range, but at middle starts to choke until I open it up more and UP goes the power. Did I miss a step in maybe the rejetting? | ||
| Swampy |
You can always pull the shim to find out, the needle height/shape is what controls the part throttle mixture. Also check ALL the easy stuff first, the spark plug wire, spark plug, fuel flow from the tank, vent tube, air filter. | ||
| Swampy |
Also, What do you mean by "bored out the head"? Do you mean you changed the intake port size/shape? If the intake port is too large you can reduce flow volume by creating a big empty hole just outside the intake valve, so when you open the throttle, it takes a while for that hole to fill in with air and flow into the head creating a bog or flat spot. An example I always talk about is the old Ford Boss 429 engine, designed for NASCAR it was ported to flow for high RPMs, the ports were so large you could roll a tennis ball down them. When we got done porting them for a 618 truck pull engine the ports were much smaller, golf ball sized and the ports were raised in the head and the port floor was raised so there was a more direct flow to the top of the valve. | ||
| Ezblast |
Is your exhaust stock? EZ | ||
| Tsunamix |
my bad, I should be more descriptive: - bored out cylinder head .10", new piston - got some work with 'good flow' on the on the ports and valves, as recommended by EZ - k&n cone filter, brand new - stock exhaust - jetted 45/170 - drilled out idle screw, in all the way and backed out 2 1/2 times - shimmed needle. new spark plug HAD a jardine exhaust on, but neighbors complained right away, so now I got a jardine w/ a QMI installed for sale and less than five miles on it (that's how fast the complaint came) (Message edited by tsunamix on January 26, 2010) | ||
| Johnnymac |
5 miles, huh? That sux! So how much for the Jardine? | ||
| Ezblast |
Your stock exhaust is choking your mid-range. You want the shim to be close to 0.05 can be a little under, not over. EZ | ||
| Kenster32 |
So if i have a free flow intake and a jardine exhaust with 48-175 jet and I'm a little flat in the middle of the throttle it could be the thickness of the shim on the needle?? ken | ||
| Ezblast |
Yes | ||
| Kenster32 |
whould you suggest thicker or thiner?? ken | ||
| Swampy |
Let me ask you a question, at midrange when it is running flat and you let off the throttle a little bit, what does the engne do, does it seem to pick up a little before it the rpms drop, you are probably running a little rich, so you would remove a shim or thin it down a little. | ||
| Ezblast |
Good question | ||
| Kenster32 |
i whould discribe it as just weaker than the top or bottom so its not way off its just not exactly right it feals like it shud pull all the way thru but goes soft in the middle but not cutting out just flat | ||
| Swampy |
Where were your needle shims at? How thick? | ||
| Ezblast |
Should be around 0.05 or a bit less. EZ | ||
| Kenster32 |
im pretty sure it was right at .05 i could try a little thiner and see if it changes well when its not forkn 3 degrees out side ken | ||
| Swampy |
UH....YEAH!  | ||
| Gearheaderiko |
.05 is a guideline. You may need less OR more shims. FWIW: I use 4 'shims' and though I havent measured it, its definitely more than .05" (I adjusted it on a dyno). Kenster probably needs more shim, Tsunamix certainly less than 4 mm. But thats just my guess! (though I pretty sure 4mm shims is way too much). Porting the head can really throw things off especially now that you're running the stock cork (kinda like buying running shows then not tying the laces). Cold weather can really change needed jetting but I'm still sure a 48 slow is way too big (but if its 3 F outside.....) DISCLAIMER: Opinions based on experience but may not be typical. | ||
| Ezblast |
Try a 46. EZ | ||
| Kenster32 |
cool i dont ride when its cold so my set up is for 65 and above my concern is to not run lean thats why i went with the 48-175 i dont think i ever smoked a motor runing rich jets are cheep so experimenting with them is eazy enough if i know how each one efects it ill admit that carbs have always been my bain and i can follow directions but if something goes wrong im stumped thanks four the help ken i fix things for a living but motors have alwase confused me | ||
| Tsunamix |
sorry for the delay. I've been diagnosing it all day yesterday and it turned out to be a problem with the carb itself, more likely the diaphragm since it has much difficulty going up and down. After trying out everything else I turned to a spare 'stock setup' carb I had laying around so I switched 'em out. The idle was very rough, very low even with that screw near the throttle cables pushed all the way in, but went back to normal after riding it for a minute. The bike ran BEAUTIFULLY for less than a mile until it suddenly died out on me. Luckily I was only a mile away from home and I went mostly uphill, so I pushed it back and rode the hill home. I narrowed that down to either the spark plug going out (it was burned out like no other) or I ran out of gas, since the tank was quite empty. Will let you guys know later tonight. I'm a bit hesitant in rejetting the new carb, so I may leave it to the pros. I was still deciding on selling the Jardine, but yes I'm selling it. Comes with a QMI and my old exhaust retainer ring stuff still on. It has some very light scratches here and there from my socket wrench tapping it during install. I love the fitment of it, but it's just too loud for me in general, even with the QMI. $260 shipped UPS sound good for anyone? | ||
| Tsunamix |
So I got it running again. Turned out the carb had slipped right off the intake boot while I was riding. lol But the problem now is the new carb. The bike runs, but now the idle hangs after I try shifting up, and as I slow down the engine pops. it also has problems idling, even with the throttle position screw in all the way. To me it sounds like a sensor may be broken in it. My other carb worked better, so what I'm planning to do is to take the parts from that newer carb and pop them in the old one, but I think I just need the diaphragm assembly. Wrong price on the Jardine. I'll sell it for $210 shipped w/ the QMI already in it. Will keep you guys posted, if you don't mind =) | ||
| Swampy |
Check your intake coupler again. | ||
| Ezblast |
Concur | ||
| Gearheaderiko |
"so what I'm planning to do is to take the parts from that newer carb and pop them in the old one" ooh, thats sounds like a bad idea  . "sensor"? There arent any except the Throttle Position Sensor and that will just mess with the timing. If you're just swapping bad parts for good...okay. But swapping parts just to be swapping parts often ends up without a working carb. Pardon my alarm, but I've just seen way too many carbs screwed up by well meaning people. | ||
| Tsunamix |
yes, swapping bad parts for good ones. On the other carb it was the diaphragm that went bad. I don't know about this one I got in now, but I'll experiment with both. Is the intake coupler that boot? I just changed it a month ago too. Oh well, good I got a spare. | ||
| Crackhead |
check the jetting on the new carb. I am thinking it has the 42 slow jet with the mixture screw turned in and 165 main jet. | ||
| Tsunamix |
never removed the bottom of the carb yet, but pretty sure it still has the 42 165 jet as the idle mix screw was never drilled out. Think 45/170 jets would fix that idle problem? | ||
| Ezblast |
LOL - that and turning the idle adjustment screw out 2 1/2 turns from bottom. EZ | ||
| Tsunamix |
so here's what I found out after taking a second look. The carb wasn't hanging idle because of sensors or damage, it was just straight up dirty! like, public toilet dirty! So I took it apart, went all out with the carb cleaner, and since I had it apart I did the rejet. I thought I had 45/170 but it actually is 48/170. I did drill out the idle screw, back out 2 1/2 turns, and shimmed the needle a little bit. Anyway, thanks for all your input. The bike runs beautifully, way better than when I first got it. It's currently at my parent's house not far from me and i'm picking it up the next day it's said not to rain (sunday) Next things I gotta do is try calculating gas mileage and putting that Jardine on eBay. |
