Jetting problems- help!
 

Greetings from a new user.

I have an 03 VTR that I finally fitted with a Yoshimura RS3 Zyclone. I just got the bike from getting jetted (Dynojet kit) with the following settings:

Pilot #50
Mains # 185/190
Needle 4th notch down

The guy who did the jetting is very well respected here for carburetion work, but the thing is a total bear to start. Even he seems stumped.

The dyno shows a nice power curve and the air fuel is perfect (12-13) from 5K up. The AF is a bit lean from 3.5K to 5K (no higher than 15).

It just takes forever cranking over to start, and requires me to crack the throttle to get/keep it going.

Has anyone had a problem like this??? Please help!

Re: Jetting problems- help!
 

I know it sound stupid, but did you verify that the choke Lever works properly? (on both carbs?)

It sure sounds like the fuel enrichment for cold start isn't working.

Re: Jetting problems- help!
 

Thanks, I will check that. Note that it's also a bitch to hot start...also, I went into my garage last night and the whole place smelled of petrol. Never smelled that strong before...what might cause that? Perhaps something is causing the thing to flood when switched off?

I had the same cold start issue after slip-ons, K&N, Jet Kit and dyno jetting. The choke cable was only opening one of the carbs - for the other carb it broke off and keeps it shut. I ended up increasing idling RPMs via idle adjust screw (to 1400 RPM). When I start, I open choke momentarily, then start, crank the throttle and hold it there at 3k RPM for 30 secs (after closing choke). Then I blip the throttle a few times to about 8k, then let it idle, then blip it again a few times. When the temperature reaches 100F, I let it idle and heat up to 120F (which virtually eliminates the clunk-die thing, esp. while braking at traffic lights). Then I ride.

Adjusting the idle screw did make the bike run hotter in stop-go traffic. It is now running at about 200F.

I haven't attempted the TPS mod fix yet (no time), but will try it when weather gets warmer.

Chocke it actually an enricher! kinda important... Remember the LESS turns out from seated with the mixture (air bleed) the richer and cooler running around idle speed .... we hope. Damned things run HOT

Re: Jetting problems- help!
 

Could be some dirt sticking the needle and seat "s" or the float height got whacked when the carbs were apart . Might want to check to see if fuel has got into the oil which is common when problems similar to this arise . Fuel will whack the viscosity index improvers and thin the oil out + a few more off topic problems like elevated cylinder wear ect .

A tip when restarting after the fuel bowls have been drained is to use an old gear oil bottle and prefill the bowls right through the main fuel line . Saves the starter and is a bit easier on the cams that get no appreciable lube while cranking .

Re: Jetting problems- help!
 

Well, we think we've identified the problem in a bad petcock. Fuel is leaking into #1 cylinder (wet plug) but not #2. Going to check it out to either rebuild it or replace.

I must say, once started I totally love having a properly jetted hawk!!

Merry Christmas all, and thanks for the advice!

Re: Jetting problems- help!
 

Drop to a max of a 48 pilot jet or go back to the OEM 45 pilot jet and OEM air filter. Check that both enrichener fittings and slides are installed properly, and for air leaks (with WD40 or soppy water). 2.5 turns out on the mixture screws should be more than adequate, and recheck syncronization with a mercury stick or electronic gage. I try to keep mine within 1 cm versus the 2 cm the manual allows; also check it at 500 rpm, around 1400 (where I keep my idle speed) and again at 4500 ~ 5000 rpm.

I'm not sure what needles your running but I just shimmed the OEM needles up .061", kept the 45 pilots, run the same 185/190 mains and set the mix @ 2.5 turns out or even less using a exhaust gas meter (not A/F). With this home brew jetting, 2Bros aluminum slip-ons, and hogged out collector restriction (opens right side up more), it was pumping out almost 103 HP and 70'# corrected on a Dynojet 250 (I think) at 30,000 miles (now at over 50k miles). I also use Mobil 1 15W-50 auto grade synthetic oil and a Purolator PL14620/PL14610 synthetic media premium auto filter (see http://motorcycleinfo.calsci.com/Filters.html).

BA

Re: Jetting problems- help!
 

"Remember the LESS turns out from seated with the mixture (air bleed) the richer and cooler running around idle speed"

The foregoing statement I do not believe is correct. The pilot/idle mixture screws enrichen as they are turned out; i.e., they are fuel not air metering screws.

BA