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rev hesitation, Keith Krause?

  • Thread starter Thread starter luc8421
  • Start date Start date
L

luc8421

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For a brief history of my bike, I've got an '85 700es, with a Yosh pipe, EMGO pod filters, and a DJ stage 3 jet kit, currently with the 134 main jets in I believe, the needle clips are on the third notch from the top. the kit is installed correctly with the correct hole drilled to the correct size, and yes, the carbs have been cleaned and rebuilt with Robert Barr's O-ring kit. The petcock has been rebuilt with a good rebuild kit including o-rings and diaphram, so there's no problem there. Exhaust seals were replaced last week, intake o-rings were replaced a month ago, and I did a valve job two months ago. I also know all the wiring on the bike is good, I replaced the entire wiring harness with a brand new OEM wiring harness, and all other little bits of wiring I've personally checked. Oh and if it matters I just rebuild the forks :P

So on to the problem. Around 6-7k RPMs, there is a hesitation while accelerating, which goes away a little after 7k. Because of how loud my pipe is, the only time I am up at this rpm is during hardish and really hard acceleration, so I'm at 3/4 throttle or more when the problem occurs. I haven't checked, but I'm pretty sure it would rev through the range without the hesitation if I were using less thottle, but like I said, it's real loud, so theres no reason to have it up there in RPMs if I'm not accelerating real hard. It does however rev through the entire rev range while in neutral just fine.

The tweaking I've done so far is with the air/fuel mixture screws which are about 3.5 turns out. turning them in seemed to help a little, but not much. I increased the needles from notch 2 to notch 3 a while ago, and it really helped the response throughout the entire rev range. If my memory serves me correctly, this problem occured after I did the valve job, which helped the hard starting problem I was having, but then gave me this problem.

I'm sorry to be so long winded, however I wanted to give an accurate and complete history so you experts could give the best advice. Thanks in advance guys. I sent a few PM's to Keith after I read about him helping out another guy with a similar problem, and now I'm taking his advice to get others involved.
 
I gotta make this quick because I have to leave.
You said the best clue: the bike rev's fine when in neutral, but not under load. A lack of fuel always does this.
If you're right at 3/4 throttle position, it could be either the jet needle position or the main. I suspect the needle. Do a solid 1/3 throttle position test for a couple of miles and chop off, read the plugs. Mark the throttle and grip so there's no doubt. If the plug color looks acceptable, tannish, I'd leave the needle alone and try a larger main. If the color is lean, raise the needle a "1/2" position by installing the e-clip one position lower on the needle and installing a jetting spacer on top of the e-clip.
Be sure the any float bowl vent lines are removed and the nipples left open (if this applies to your carbs).
Carbs are vacuum synched too?
 
alright keith, I did what you said, raising the needles by lowering the e-clip one notch. currently the set up is as follows. I've got two washers, one is the size of the e-clip, the other is the size of the little spring, I've also got the plastic spacers.
so I've got, from top to bottom, spacer, e-clip(4th notch from top) small washer, larger washer.

I'm going to wait until later tonight or tomorrow to install them, but if this is the correct way to do it, then here goes nothing.
 
luc8421 said:
alright keith, I did what you said, raising the needles by lowering the e-clip one notch. currently the set up is as follows. I've got two washers, one is the size of the e-clip, the other is the size of the little spring, I've also got the plastic spacers.
so I've got, from top to bottom, spacer, e-clip(4th notch from top) small washer, larger washer.

I'm going to wait until later tonight or tomorrow to install them, but if this is the correct way to do it, then here goes nothing.
Click to expand...
OK. So I take it you did the 1/3 throttle test and the plugs say lean?
As for your jet needle assembly order, I don't have your models manual, so I can only tell you what I think is the right order of the spacers, clips and washers.
Your stock plastic spacers should be re-installed with any jet kit needle in the same order they were on the stock needle. If one stock spacer was thicker or larger than the other, it must go back in the same location it was. If one is larger than the other, the larger one usually goes on top the e-clip, the smaller below. The metal DJ jetting spacer (when needed) always goes directly on top the e-clip. So the finished assembly would be: stock larger spacer...over the jetting spacer...over the e-clip...over the smaller stock spacer. Verify this if you can with your manual.
If the jet needle e-clip was in position #3, then to richen the mixture "1/2" a position, you would put the e-clip in #4 position from the top WITH the jetting spacer on top the e-clip.
I'm only guessing a 1/2 position change is necessary because the hesitation sounds minor and limited in the powerband. I'd have to see the plugs myself to help decide if a full position richer was a better choice.
 
alright, I got the carbs off, richened the needles, and reinstalled them all within an hour. (boo-ya pods!) I went for a very short test ride, half a mile round trip. on the way back, going up decent hill is when I tried accelerating again. There still seemed to be a little hesitation sound, yet it powered through it better then before, and it seemed like the hesitation was more like 5k-7k this time, but like I said, not as much as before. If I'm going 25mph up a slight hill I need to drop it to 2nd in order to be able to slowly lay on the throttle. otherwise even if I just barely give it some gas, say in third gear, it'll start bogging out, definetly sounds like it's too rich.

so with these scenarios, does it sound like the needles are now too rich? or maybe I need bigger mains? or perhaps I should figure out how far out my air/fuel screws are, and tweak those? but I seem to remember that they're only for idle adjustments.
 
First of all, there's the question about the correct order of the stock spacers and the placement of the jetting spacer. You didn't say if you have this right. If these spacers are reversed or in the wrong order, re-jetting will be impossible. You have to verify this.
Then, you seemed convinced and you did describe a lean condition before the (I assume) 1/2 position richer needle change. Now, after just a 1/2 position change you think it's rich. This can't be. Somethings being lost in communication here.
You say the carbs are cleaned, rebuilt, etc. The vacuum orifice to the diaphragm chambers has been correctly enlarged per the jet kit instructions? Any larger springs installed? Did you check the float levels and vacuum synch the carbs? This must be done also as part of any re-jet. Also, remove any float bowl vent lines when running pods.
If all the above has been done, including the correct needle assembly, then do the 1/3 throttle position run for a couople of miles and get plug reads. If your spark quality is good and timing too, the plugs don't lie. As the color gets closer and closer, the performance will get better and better.
It's the only way I know how to jet or to tell someone how. If you go up small hills at 25 mph, I can't tell you what the needle circuit is doing.
 
well keith when you're right you're right. I know I need to go on a much longer test ride, I wish I had done that today, going to work, however the weather man predicted rain, even though none came! very frutrated.

As for the spacers and such on the needles, I can't tell you if I've even have the stock spacers, because I got the bike with the DJ kit installed, and I have no idea what the true stock needle pieces are. I'll try to describe them better though.

I've got a plastic spacer, about a quarter of a centimeter thick, and two washers, each about .5mm thick. When I originally came into the post, I had the spacer, the e-cip on the 3rd notch from top, and then the two washers. I then changed the e-clips from the 3rd notch to the 4th. I realize this is a full clips position, not just 1/2, but I didn't realize it until I thought about it later.

I'm going to ride to work tomorrow, rain or shine. so hopefully I'll have a better answer for you by then. however before I go to work, I'd like to lean out the needles 1/2 a notch, so I'm at 3.5, not 4.5. what's the correct order of spacers and washers to do this? I'm thinking puting the e-clip back to the 3rd notch, but puting the spacer below it, with the washers above the e-clip, am I way off on this?

I doubled checked, and the mains are 134s, the hold in the diaphram is drilled correctly, and I'm also going to reset my air/fuel screws to 2.5 turns out, does this sound advisable?

I'm sorry if I'm giving you frustrating answers, however I live in an area where this is a lot of hills, so it's really scary going out for a test ride when there's a good possibility your bike isn't jetted correctly to give you the power you need to get back up the hill and home.
 
I don't know what to think about the order of your spacers, etc. You'll need to find out.
It doesn't make any sense having the two identical .5mm washers together like that.
Since you want to lean the needle a 1/2 position, all I can do right now is work with what you say you have, assembled right or wrong.
If you now have the e-clip in position 4 from the top with the stock spacer above it, simply leave the e-clip where it is and place the DJ jetting spacer on top of the e-clip. You'll then have, from the top, stock spacer...above the DJ jetting spacer... above the e-clip... above the two .5mm washers. This will be 1/2 a position leaner, or the same as position 3 1/2.
The 2.5 turns out on the mixture screws sounds Ok for the time being.
Did you say the float levels have been adjusted and the carbs vacuum synched? You can't re-jet accurately without these being done correctly.
 
sorry, I forgot about those two things.

yes they're synced, and yes I believe the float bowls are set correctly. from the gasket surface (with no gasket of course) I think I set them to 22-23mm. sorry about the vagueness, I did it a while ago according to my factory service manual.
 
luc8421 said:
sorry, I forgot about those two things.

yes they're synced, and yes I believe the float bowls are set correctly. from the gasket surface (with no gasket of course) I think I set them to 22-23mm. sorry about the vagueness, I did it a while ago according to my factory service manual.
Click to expand...
OK. Just realize that correct jetting depends on many things.
If one thing, or a combination of things are just a little off, you'll be blaming the actual jet size or needle adjustments you made instead of the true problem. This will lead to everyone wasting their time and the motor can end up being damaged too.
 
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