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Jetting issues after installing TT recommended settings...


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Hiya,

l am now on my 3rd set of carb adjustments. When the bike came to me it had an E model FCR 39/434 BB/E cams/E cdi/E air box/DEP exhaust.

The settings at that time were...

150 main jet

45 pilot jet

65 starter jet

200 main air jet

60 pilot air jet.

Fuel screw 2 turns(Works Connection)

The bike ran OK but not great. l had the SSW/MRD installed and the bike ran like a bag of chisels. With a Works Connection fuel screw, a 38 pilot jet and a 160 main the bike would really lunge at the beginning but the top end was lacking. l came here to ask about my jetting after installing the quiet insert and William pointed out that the WC fuel screw could be part of the problem. Noble also stated that a 155 main jet would probably be better due to the quiet core. He also said that l needed to change the 60 pilot air jet to a 100 air jet and return to the 45 pilot.

So... now my settings have been changed to...

155 main jet

45 pilot jet

65 starter jet

200 main air jet

100 pilot air jet

Fuel screw 2 turns(Keintech)

The bike runs well. To be honest, l have no beefs with it... however, the tech who did the work thinks that the bike is running a touch lean just off idle and recommends a 95 or 90 pilot air jet. My race coach tested my bike with both settings(38 pilot/160 main/60 pilot air/WC fuel screw vs. current settings) and said that, although it runs better overall, it had lost some of the "just off idle" punch it had with the earlier settings. He also recommended testing a 90 pilot air to recover that initial lunge when cracking open the throttle.

For the kind of racing l do, there is an awful lot of WOT and then slamming on the brakes... almost entirely in 1st gear. l'm in my second year of gymkhana riding and the DRZ has become quite a popular weapon of choice. Most guys don't do anything to the bike in terms of power mods, as the standard carb is less peaky than the FCR. l am trying to dial in my FCR as well as possible for max torque just off idle and no bogging from rapid, repeated full open-full closed throttle usage.

By the way... l live at sea level and it is currently summer mid-high 20's celsius and moderate humidity here in Japan.

Any comment on the move to a slightly smaller pilot air jet... and perhaps a move to a 158 main jet would be greatly appreciated!

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anything that happens while the throttle opened or being opened has nothing to do with the circuit.

what have you done to the accelerator pump?

does the idle react to the fuel screw properly?

what need are you running?

the title of your thread is misleading.

Hello Eddie,

Thank you for your post. l have done your mod to the accelerator pump. The linkages have been wired together and the diaphram has been ground down. l have the Keintech needle in the carb now and the idling is reacting as it should.

l have an EMN needle in the carb with the clip in the 3rd position counting from the top. My coach said something about trying the 2nd position however he also said it is better to do one adjustment at time.

Before l do anything l wanted to come back here and see if it was possible that l overlooked something. Thanks for taking the time to read ­čśĆ

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Sorry Eddie...

Part of the problem is l am living here in Japan and l don't speak Japanese very well. l have the tech at the Suzuki dealer telling me one thing and my coach telling me another... both of them using the kind of terminology that doesn't exactly show up in your typical language class.

l wrote down the base settings from TT for sea level based on an open pipe and sent them to the dealer where my bike was getting worked on. They installed all the jets that l requested... however when l picked it up the tech said that, in his opinion, it could do with a slightly smaller pilot air jet to improve initial response just off idle. l don't know whether he had his nose out of joint because l chose to go with settings that weren't his or if he was genuinely trying to help. Sometimes it's hard to tell what is going on behind the words.

My coach simply said that there was more punch with the previous settings(160/38/60) and that the bike was running a bit lean or a bit rich just off idle.... but it was close. He went on to say that when it's close it could go either way and it was hard to tell which direction to go without testing a few different options. He agreed with the Suzuki tech that a 90 pilot air jet would be the first thing to try. The leaner needle comment was sort of an afterthought in case the jet adjustment made the situation worse instead of better.

Anyway... regardless of what they both said, my experience is this: l was at my first race last Sunday and Monday. As l had mentioned before, l basically go from rapid WOT to complete shut-off while slamming on the brakes to WOT again over and over in a 2 minute span almost all in first gear. The bike will pull fine but the initial response when l first open the throttle is slightly delayed followed by a strong lunge. A few times the bike seemed to gurgle a bit when l first cracked the throttle but it cleared itself out as the revs built.

When l ride the bike on the road l can't find any fault with it. These comments are based on a very specific situation and type of usage. From my coach's perspective, the more off idle pull, the better. A bike that pulls well just off idle will be smoother exiting 360's around cones without lunging like a wild horse to the next cone.

l wanted to run all this past you first before doing anything more to the bike. l don't fully understand how a carb operates and l am sorry if l am making ridiculous statements to those who know better. l don't... which is why l am here. ln the English speaking world this is THE place to go for DRZ info. You should have seen the look on the faces of the locals here when l showed them your mod to the carb! They all wish they could speak/read English so they can access this site.

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if the idle reacts to the fuel screw correctly then going to a 90 pilot air jet will just make the idle rich. this is why you changed your jetting to begin with.

sounds to me that niether on of them knows what they are talking about.

what needle did you have before?

if you want to make just off idle richer you need a EMM needle.if you want to make it leaner you need a EMP needle.

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There has been an EMN needle in from the beginning. lt came to me with the EMN needle. l am making assumptions that the idle reacts correctly to the fuel screw because of what l was told, not through personal experience.

The bike is here at home with me now. Should l check the number of turns the fuel screw is at?

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  • 2 weeks later...

Hi Eddie,

Sorry for the massive delay in replying. We've had boatloads of rain here to start with and then l wasn't able to turn the damn screw! l posted a thread on tips/tricks to get at the Keintech screw and now l have been able to adjust it.

To start with... amazingly... the screw was about half a turn from being ALL the way in! The bike would bog a little if l cranked the throttle in neutral but would rev up nicely after. In gear it would stutter a bit if l held steady rpms and the initial grunt from a standing start or a slow tight manoeuvre was a bit lame. l have now wound the screw out to exactly 2 turns and the hesitation l felt seems to have reduced. l didn't get a good chance to test it out very well but my initial feeling is that when l am pulling away from a set of lights there is more pull from a standing position than before. Once l get it nice and warm l will adjust the screw to see if the bike runs better at either + or - the 2 turns out setting.

l don't know what part of "fuel screw 2 turns out please" is so hard to understand. l am absolutely positive l can say that in Japanese!

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Yeah my confidence has been rattled as well. Unfortunately it's the old "devil you know or the devil you don't" scenario. l don't have any experience working with another shop and they didn't do a bad job with all the work they've done to my GSF 1200.

Although the #90 and #95 pilot air jets have arrived l am going to do NOTHING until l can report back with my findings re: fuel screw adjustment and idle reaction when the bike is at proper temperature. l bet that those two little jets will end up collecting dust in my drawer now.

Thank you for your continued guidance!

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Hi Eddie,

OK... a few new things. The fuel screw does not seem to make that much of a difference unless l reach the max at both ends. lf l turn it all the way in, it will begin to idle at higher rpms. lf l return to 2 turns out and then keep backing it out, the bike finally stalls at about 3+ turns out. This is when the bike is hot enough for the fan to turn on.

l rode the bike hard today and only when it is hot do l get the bogging. lt happens from a stand still or walking speed... if l crank open the throttle like l am trying to get the holeshot or tear off from a set of lights, the bike will bog through the first 1/8 or 1/4 turn of the throttle and then run strong and clean to the rev limiter. l went ahead and tried the #90 pilot air jet(for $80 worth of tech time...aaarrrggghhh!) and the bike runs worse than before... so that is obviously not the answer. l have tested the bike with the air box cover off with both the 100 and 90 jet and it made it worse.

So far the bike has run best with the very first settings.... 38 pilot and 60 pilot air... no idea why. l would like to get rid of this bog before my next race on the 14th-15th so l have a little time to sort it out. Hopefully we can get to the bottom of this within a week (:banana:)

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its rich on the pilto circuit and going to 90 pilto air jet made it worse.

why if the fuel screw tests indicated it was rich would you make it richer?

the aluminum fuel screw is the issue. they are junk and not machined correctly.

put the 100 pilto air jet back in and go a 42 pilot jet and retest the fuel screw reaction.

or i would get a good fuel screw.

also the tech told you it needed the 90 pilot air jet and got you going on that ridiculous idea. so now you did it,it made the bike worse and he charges you $80? i think you need to have a chat with him on that.

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Hi Eddie,

There's a Kientech fuel screw in there now. l pulled the Works Connection screw out and had them install the Kientech screw when l went to the 45 pilot/100 pilot air jet combo.

Should l still try the 42 pilot?

There's another place in town that does full carb analysis on a Dynojet rolling road.... but they charge something like $500!!! At that price l may as well just buy another carb.

Could l have messed up the carb mod with the wired linkages/ground off diaphram stopper?

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OK!

The 42 jet is ordered. Unfortunately it won't be here until sometime next week because the whole country has a three day holiday starting on Thursday. They are going to put the bike back to the previous settings(38/60) for free so l can at least get through the races on the weekend.

Next week l will report back with news on how the bike runs with the 42/100.

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OK back again...

The shop put the settings back to 38/60 and the EMN needle on the 2nd clip. l rode it out to my practice area and in all ways performance-wise it has improved. There is no stuttering when taking off hard at a set of lights or accelerating hard from a slow manoeuvre.

However... the fuel screw doesn't really react to anything other than extreme out. When l tried to adjust it l found it at 0.5 or 0.75 turns out. l screwed it all the way in and nothing changed. l screwed it out more than 3 turns and only when l was worried about it dropping out did the engine stumble.

The bike also seems louder than with the 45/100/3rd clip combo and may be vibrating a little more than before... but the power difference is definitely better with the current settings and the slow-speed-then-hard-on-the-gas stutter is completely gone.

l left the fuel screw at whatever setting they put it at since they set it up with an emissions tester. l don't want to do anything until you have read and commented on these latest developments.

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38/60 is too rich as well if it idles with the fuel screw fully in.

it doest really matter how you get there,but its gotta have proper fuel screw reaction.you either gotta reduce the pilot jet size or increase pilot air jet size.

in order for the 38 pilot jet to work you need around a 75 pilot air jet.

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