When I Whack it, it wants to die


I know the quick answer to this is an Edelbrock, but I can't afford it. Lately, it seems worse, that when I whack the throttle, my bike wants to bog down. Could this just be a dirty air filter? I uncorked it last year, and have had no issues. I don't think I have a vacuum leak. Would going up a couple of sizes on the main help? I have a 170 in it now, and I think I have a 172 lying around. Any suggestions?


Winkel :cry:

I will sum it up the best I can. When you wack the throttle the bike goes real lean because it can't pull the fuel throught the jets fast enough. You are way to lean as it is making it worse. Better for power when you are up and going but, you need to compormise. 68s is ok, but the 70 or 70s pilot is way better. The bike will be easier to start. Th b53e needle helps. but, doen't fix it. A bigger main jet realy helps get rid of the dead spot when you wack the throttle. They don't cost that much to get two more. Get a 175 and a 178. You can change a main jet from the bottom of the caruretor. The is a plug on the bottom that is a 17mm. Inside is the main jet that takes a 6mm socket. I know you know this but, just in case someone doesn't. and see that the dead spot is all but, gone. The reason for this is the bigger main jet lets you pull some extra fuel past the needle as it raise when you wake the throttle. It is a little give and take. 4th clip down on the needle. Heck try a 180 main ****This would not be good because you will be to rich for your setup. It will show you that it works though. But, if you have all the holes in the side cover, No-toil or Uni air filter, opened up exhaust (header and muffler) you can run a 185 main and really get rid of more of that dead spot.



What altitude are you riding at? Once jetted correctly, whacking the throttle on a bike that has no pumper carb as stock equipment may still bog, since there is no accelerator pump involved. You can spend the money on a pumper carb, and whack away, or quickly roll on the throttle instead of whacking it open, and get no bog. A very quick roll on with the stock carb will not cause a bog. And since the 650R is so powerful already, you really have to weigh any added benefit between whacking it open suddenly against quickly rolling it on. Overall riding skill and style will overtake any benefit of just whacking the gas open suddenly, in my opinion.

Four-strokes generally don't like to be whacked open suddenly if they don't have a pumper carb, especially at very low rpm. It's really just a matter of adjusting riding habits to cure the problem. Or get a pumper carb.

There is a very fine line between very quickly rolling it open, and just whacking it open. And it makes all the difference between getting the bog or not getting the bog.

Jetting rich on the main circuit helps, but requires more air intake, such as drilling the side panel/airbox.

What you said "Smashin" :cry::cry::cry:

:cry: You guys really know you shit!!!!


Thanks for the replies. I do most of my riding at about 700 to 800 feet, South central Illinois, or Western Kentucky. I'll try the bigger main jet first to see if that helps. I have a 175 in my spare parts drawer.

Thanks for the help, I'll repost with the results when I'm finished.

Thanks again,

Winkel :cry:

I tried to believe that the stock carb was acceptable as well. I've ridden big thumpers without pumper carbs for 20+ years. I didn't need no stinkin pumper. I didn't even notice the hesitation until a fellow big thumper rider (that used to race KX500's and CR500's) said "what is wrong with this thing". I still didn't have a problem with it. This summer that all changed. We went to Colorado riding and I knew I would have to rejet going from 900 to 12,000 ft. No problem I have quite a collection of jets on hand from 160 to 185 main, stock pilot jet, 68s and 70s. 2 different needles and seats. To spend half of your riding time rejetting trying to get the same performance you got at home SUCKS!!!. I know your going to lose 30% of the power at altitude. I got it to run clean from right off idle to wide open but it would surge right off idle but that initial hesitation became a liability in the mountains. It wasn't too long after I got back that Barnum's ran the $350 special on the Edelbrock QS. It took 1-1/2 months to even get it. It was worth it. There is no comparison. Your kidding yourself if you think the roll-on is as good. I haven't even used it for the reason I bought if for YET. No rejetting at altitude. I can't wait. Forget all the other talk about easy starting, running on its side etc.. That didn't matter to me, I've never had trouble starting it. It just runs that much better period!

From idle you could kill any 4 stroke if you opened the throttle fast enough. :cry: Pumper carb or not. I have a 525 KTM with a pumper that flat rips but you can still kill it if you "whack it open" fast enough. I would like to know the situation during a ride where that is ever required anyway. I might get the Edlebrock if I had drastic elevation changes. That aspect of it seems cool. What carbs are the Honda teams running on their Baja bikes?

I can guarantee that you can't kill mine no matter how fast you twist the throttle. That was the whole purpose of this experiment! I can guarantee that It WILL put you on your butt if your not careful. The throttle response afterwards is instantaneous or you have the pumper set wrong.

Team Honda uses what Honda sells. Team Honda uses the stock skid plate so do others before the first hole in the crankcase. Team Honda gets free parts.

I've never ridden Baja and I don't know if you need that instant throttle response to get over a log or rock but I find it quite useful where I ride.


I wear glasses as it is............. My dad told me to save it until I got married. I've got a couple of gallons now, and I don't know what to do with it...Oops, wrong forum...

Anyway, I swithced to the 175 main tonight, and it does seem a little better based on the short ride I took. The brief hesitation was noticeable when I first got the bike, but it really doesn't bother me now that I've adjusted to it. I just wondered if there was anything that could be done (cheaply) to make it better.

Thanks for all the input!!


P.S. The title was intentional, to get more attention to my question.


Another question..

I've seen mention of the 70s pilot jet. Does this help much with starting and whackability? My bike starts fine, and all of the other recommendations were for the 68s. That is what I have in it now. Any thoughts????


Winkel :cry:


You will only go blind if you don't wear goggles :cry: No really, I I've seen this problem when I had my XR600. If I whack it with no load (not in gear riding it) It would bog and die. Riding the bike it didn't do it but at low RPM it could stall going up a hill. I fixed my problem by raising the needle one notch. Jetting didn't really help much or caused other starting problems.

You said the problem seams to be getting worse. It must be real cold in your neck of the woods compared to summer. That will have an effect on the bike too. With my XR650R I don't have that problem but with the air cooled 600 it took many hours to get the bike to run right. I found that the pipe made the biggest difference. I ran an FMF for a couple of years then went to WB's pipe. The FMF was faster but the White Bros pipe sounded better and jetted easier.

Yes, a 70s will make it start easier and help reduce the hesitation, dead spot go away. But, if your bike is not opened up more it will run just a little rich at idle. Like I said, it's a trade off. You are trying to add more fuel when the vacuum is low to get rid of this dead spot. Once the vacuum is up now you don't want it. That is why the pumper carburetor works so well. When you wack the throttle the pump squirts while the vacuum is low. You don't have that so, you are barroing it from the pilot and pass the needle.

If I whack it with no load

Heh.....Heh.......Heh....... he said whack it and load in the same sentence :cry::cry::cry::cry:

Heh.....Heh.......Heh....... he said whack it and load in the same sentence :cry::cry::cry::cry:

They call that a Vasectomy. :cry:

If the bike's runs well before, it wont be a jetting hassle. Clean the airfilter, clean the carb, put in a new sparkplug, check the valve clearances. Good luck Winkel!

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