Patchy mid range power due to jetting?

If you are crusing in 5th gear at 50 to 60 mph on level ground you cannot be above half throttle??? You need to mark your throttle and see where you are really at. I would believe you are below 1/2 throttle and the needle transistion along with a little lean on the pilot is the problem. This bike in all years has a slight lean condition right at the transition from the straight to the tapered section of the needle. Some bikes show this condition more than others but its there.

You will notice this most in crusing conditions and not so much when trail riding.

I would suggest uping the PJ from a 42 to a 45, experimenting with the fuel screw in quater turn increments starting at 1.0 turns out. Also adjusting the needle one clip position at a time as previously suggested--Probably would be best to dump the DQR needle in favor of a "E" needle as previously suggested by James Dean.



I get the impression from you blokes that the needle fitted from standard is second rate in comparison with the EKN needle. Would I be right in guessing that this would be a better basepoint to start with before doing the fine tuning?

your like a boy with two ice creams!

you can soon get your bike running well if you actually start DOING something instead of talking so get out there & get it sorted.

there's nothing wrong with your needle. it's the most perfect needle god ever made, if i could afford it i'd have three!

does it make you feel better to know that i have a DVP in mine at the moment due to the bike producing TOO MUCH power in everything but a dry straight line (neither of which actually exist do they?).

your DQR is infitesimaly leaner at tickover (P for me is R for you).

as far as the meet & two veg of it goes your clip position is 2 1/2 clips richer than my DVP (Q to rstuv=5, that's two letters to a clip move OK?)V for me Q for you.

so if JD reckons on clip 3 or 4 for the DVP he will say clip 1 or 2 for your DQR.

like that low & behold your needle needs dropping as somebody (i forget who, but he didn't even know your needle code when he opened his gob!) mentioned higher up this thread.

the americans IMHO opinion run their bikes a clip or half a clip richer than we do/should. i don't know why. i put it down to our extra moisture content.

so try dropping the needle one clip at a time & keep testing the bike at the speeds you mention plus your rolled on thrttle tests. if you create another problem whilst curing this one, just be honest & we'll help you sort it. just don't lie to yourself about your tests. be objective.

because your a novice jet changer go for the "try it for a long while to get a true picture attitude".


Cheers Taffy,

I've been waiting for my eyes to be peeled open,I'll give it a go tomorrow in my lunch time, and I'll be giving it some scrutiny over the next week.

I'll let you know how things go.


G'day all,

Re-read the FCR jetting manual at lifenet it explains how selecting the correct pilot air jet can resolve lean/rich conditions while at constant throttle.Could this be your problem? :)


Taffy. The increase in MJ was do to the plug looking lean. This was right after a street cruise at high speed. The PJ move to 48 was suggested because of burbbling over whoops at 1/4 throttle. Sonny.

I'm not a Bloke but an individual who like James Dean and Taffy spends a hell of a lot of time and energy on this sport taking careful notes and reporting my observatins. Hopefully it is beneficial so some. I agree with Taffy that some jetting discrepancies exsist world wide--as I have stated many times before your milage may very.

But you will never know unless you take that carb appart and experiment a little. From what I'v have experience on this forum you get basic and solid advise.



Cheers Taffy, I liked the flavor of that last post! or was it two flavors. :)



sometimes a man has gotta do, what a man has gotta do!

i'm pretty much. correction.

i AM the only bloke who's saying the following



it could take a year, but eventually one or two people are going to come around to it.

go to a 45 Pilot Jet. buy a Pilot Air Screw & adjust it to the equivalent of a No125 PAJ. this gets rid of the "burbling".

i was hoping you were a "bloke" clark. they are men that you would meet "down the pub" or your "average joe". i can't say "guy", i know it's ok for you but in the UK it is a bit of a trendy thing started by the pop, fashion & model world. & you meet the nicest guys in the women's fashion industry wherever you go in the world, right!

so you keep using it, no problems, but for me it's like something crawled up my back!!!


[This message has been edited by Taffy (edited 04-20-2001).]

(just to start the conversation, I'm a bloke. A Guy is something we throw on a bonfire).

Well.... I dropped the needle 1 clip today, I'm going to give it a thorough test tomorrow, but judging by the riding I've done today, I'd say the bike revs a little cleaner through mid to high revs. The same patchiness when sustaining constant speed around 60mph (guessing the speed as the battery in my panoram computer seems to have died), in fact maybe the patchiness is a little more noticeable. I'll get a battery for the speedo tomorrow and try and get an accurate measurement of the speed and throttle position.

I'm not too bothered about the patchiness as long as it's not detrimental to the life of the engine, but if I can eliminate it in time , all the better. As has been already said, its not even there unless I'm at a constant speed on a dual carriageway.


Taffy/ Jame Dean,

I've given it a good test, and although it seems a bit cleaner reving, I think I preferred it as before, because the constant throttle problem seems to be more noticable and also the bike is generally behaving leaner. Its giving a backfire during decelleration, and when starting in the morning, I have to keep the revs up in order to keep it from stalling till it gets warm, where as before it was fine from cold.

Any ideas where to go from here?

For ref: I have main jets #160 and #170

and pilot jet #38 at hand.

Thanks in advance.



Did you try turning out the pilot screw? The #42 pilot may need serious adjustment - 1 1/2 - 2 - 2 1/2 ? Then a #45 pilot jet.



first of all does this mid range chugging only happen in 5th? try going down to 4th & at the same revs. what happens?

lower your needle one more. also open the pilot screw 1/2 turn (the one under the carb). if that doesn't work i'll be suprised.


Thanks for the help James and Taffy,

I'll have a play this weekend.




Who made you God anyway?No wonder there was a revolution and we celebrate the 4th of July.This patchiness that everyone is talking about is a lean condition and the last time I checked, dropping the needle don't improve a lean problem.I' ll bet everyone who has this patchiness problem,if they listen real close,down by the motor they will hear a destinct knocking or pinging co-ordinated with the pathy exhaust.Its called DETINATION!!!!!!!!!!!!

listening real close down to the motor's not so easy at 60 mph!

dunno about the rest of them, but theres no sign of pinking (pinging for yanks) or detonation on my bike.



-Both Taffy and Derek are riding in the UK. Taffy has experience with a similar exhaust and a whole lot more with jetting bikes. He knows what the needle code DQR means in terms of diameter, clip position, taper start, and degree of taper.

-Taffy has 743 posts on ThumperTalk!

-Dana, you have.... 4 posts :)

This thread is all about helping Derek out. Please be patient and read the posts carefully and we will all learn and benefit.



Sorry if I offended you or your bud Taffy.I really don't care how many post anyone has.Does seniority give anyone the right to humiliate and more or less demand superiority? I could go on about how much experience that I have with motors and jetting but I'm not after any noteriaty.Trust me I do have alot of experience.You yourself said that this patchiness problem could be a lean cond.Does Taffy's {dropp the needle}solve a lean cond.?Let me ask does a motor that is to rich at a steady throttle position instantly come to life with throttle application? Especially when this motor is equiped with an accelorater pump?Or does it take a while to clear out? I realise that these chaps are in the UK with a differant bike set-up,altitude,moisture,etc.I'm sure Taffy can help this boy better than I but I had the same symptoms with an American bike at 4000ft.It was bone stock and with out a helmet I could hear detination.I was affraid of opening up the exh,air box,without some jett changes.I went on a recomendation from somewhere on this sight to 48 pj 175 mj stock needle ,for insert out,air box lid off,and Yz timing.We built our own insert after carefull observation of the baja des insert and have had the air box lid on and off with only determining that it was noisier with the lid off.Right now it seems alittle rich in the pilot {48}with fuel screw 1/2 turn out.No choke needed for cold starts.I beleive when I go to the 45 pj I might want more fuel in the mid range{needle}.I hope this gives Derek some food for thought and sorry that we might have gotten off on the wrong foot. I respect all the research and development that all you blokes have offered .We are Western Fabrication Specialties in MT .We build 4130 chrome moly tube chassis snowmobiles for the steep and deep.We developed an insert for the WRs that we feel is pleasingly quiet and flows good.Hopefully we can help one another. Contact us at


No harm done here. The standard needle should be workable. Past experience and the needle codes indicate a step leaner if anything, maybe not 2 though. The richer pilot jet (42 stock) or at least turning out the screw deserves some experimenting. The problem with the stock needle is it will vary from lean to rich to lean at different throttle positions. It is hard to say whether rich or lean is the problem without knowing the exact position. We have covered this in hundreds of posts and studied nearly every aspect of the carb beyond reason, always looking for more. Try a search on EKP or PAJ to get an indication. Just as it happens, you came to the party a little late, but you're welcome to join in. :) Taffy has a way with words that some may object to, but it's well intended. Makes for better discussions and keeps things interesting.


Just heard today about a wire, if clipped eliminates the chugging I'm hearing described in this post. I'm learning the electrical system on this thing. The yamaha service guy was speaking with the regional service tech and apparently got this information. It has something to do with the emissions requirement and causes the 4th and 5th gear stutter described by many of you. I believe he said it was the gray wire coming out of the CDI. When I get a better description I'll share more.



Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now