jkmr1 Posted July 27, 2014 Report Share Posted July 27, 2014 Recently I became the proud owner of a 2014 JTG 300. I am really happy with the bike in general, however I would like to improve the fueling if possible to overcome a slight lag just off of idle. I should also point out that I may be being perhaps a little to fussy as the lag is by no means terrible. However I have been spoiled by having an OSSA TR280i with pretty much perfect fueling. To date I have tried multiple jetting, clip position, idle screw and slide changes with no real improvement from standard. (120 main. 35 idle. 270K emulsion tube. 60 slide. 36 needle) The bike is also now fitted with a low compression head to combat pre ignition issues. Running 98 octane fuel (Suposably). Altitude is sea level to no more than 500 meters. Based in Brisbane Australia. Winter at present so conditions are warm and dry. I will keep trying but was hoping that someone has come up with the magic combination and would be willing to share? Or just let me know that I am being too pedantic (possibly), and will never equal EFI perfection. Any suggestions gratefully received. (Perhaps Jotagas would care to comment?) Cheers Quote Link to comment Share on other sites More sharing options...
telecat Posted July 27, 2014 Report Share Posted July 27, 2014 (edited) Took us a while to get the Kehin working right and the settings are different to others we know about. Steve Saunders suggested that the Boysen Reeds help the "snappiness" but whether they would help in this case I don't know. I think now that the Ossa has been sorted the EFI system is going to be unbeatable on response to be honest. Why nobody else has fitted it I don't know. I was expecting there to be a GasGas this year and rumors about the Vertigo and TRS are all unsupported at the moment. Edited July 27, 2014 by telecat Quote Link to comment Share on other sites More sharing options...
jkmr1 Posted July 27, 2014 Author Report Share Posted July 27, 2014 Hi telecat, What improvement did you gain via the fitting of a Keihin (and what prompted you to)? I did consider going this way (and still may) but I was informed that the benefits are gains in mid to top performance with a sacrifice in initial response and bottom end. Would you agree? Cheers Quote Link to comment Share on other sites More sharing options...
telecat Posted July 28, 2014 Report Share Posted July 28, 2014 My Son Rides it and is a "bottom end" rider but does use the revs when necessary. He reckons the entire rev range is better with a Kehin. You do need to fiddle more though as they are more sensitive to the conditions than the Delorto. It is an expensive fix and we had a Kehin already so it was not difficult to swop. Quote Link to comment Share on other sites More sharing options...
jkmr1 Posted July 28, 2014 Author Report Share Posted July 28, 2014 I may give a Keihin a try if I am unable to improve things with the Dellorto. Would you be willing to share your set up for the Keihin? Slide, jets, needle etc? Did you have to change or modify anything in order to fit the Keihin? Cheers Quote Link to comment Share on other sites More sharing options...
telecat Posted July 28, 2014 Report Share Posted July 28, 2014 (edited) The Kehin fits with a little fiddling. For Settings we started with Main 125 Pilot 48 Slide No. 3 Needle JJH Clip 4th down from the top Air screw 1.5 turns out from full in. Which is what Ross Danby and Richard Timperley run We then fiddled and ended up with a 3.5 slide Pilot 45 122 Main Clip 3rd down from the top. Most expensive to fiddle with is the slide as they cost a bit. I think Jordi Tarres preferred a 128 Main. They do have a wide variation of settings that can be run. We use Shell or Tesco 99RON fuel with a full synthetic GRO two stroke oil. Edited July 28, 2014 by telecat Quote Link to comment Share on other sites More sharing options...
arnoux Posted July 28, 2014 Report Share Posted July 28, 2014 There is a specific Keihin inlet manifold/red block available as a OEM part. (part #2303321) Apart from the PWK carb, the parts required are throttle cable, and this inlet manifold/reed block. Quote Link to comment Share on other sites More sharing options...
jkmr1 Posted July 29, 2014 Author Report Share Posted July 29, 2014 Thats great info. Thanks Quote Link to comment Share on other sites More sharing options...
lineaway Posted July 31, 2014 Report Share Posted July 31, 2014 I would try a 36 or 38 pilot. Quote Link to comment Share on other sites More sharing options...
jkmr1 Posted July 31, 2014 Author Report Share Posted July 31, 2014 Tried a 38. It was worse. Best was a 31 for minimising the lag but was then too lean during transition. I have fitted a #50 slide to increase velocity and richen it during the transition phase. Haven't tried it out yet though so no idea if it will help. Also ordered a Keihin today so will give that a try. Quote Link to comment Share on other sites More sharing options...
dadof2 Posted August 2, 2014 Report Share Posted August 2, 2014 If you don't mind risking having to buy a new carb slide try increasing the cut away your present one by about 0.4 to 0.5mm. It only takes a few minutes with a file. Do it by increasing the angle of the cut away, don't move the point at which the cut away meets the base of the slide. Quote Link to comment Share on other sites More sharing options...
jkmr1 Posted September 17, 2014 Author Report Share Posted September 17, 2014 After trying multiple variations of jetting and slide changes in the end I gave up on the Dellorto. I just couldn’t get rid of the slight lag and I also felt that it was restricting overall performance. As a consequence I bit the bullet and bought a PWK Keihin, new reed block and throttle cable. Fitting was not at all straight forward. The Keihin is shorter, the float bowl and especially the drain outlet fouls on the engine casing. The breather is pushed up against the exhaust and cuts of the air flow and you are unable to level the carb! Oh, and the cable entry doesn’t seal and leaks water into the carb when washing the bike. So modifications are required to enable fitting. Firstly had to make a 6mm reed block spacer to push the carb back and up off of the casing. Removed the bottom carb drain and drilled out the vent on the LH side and blocked off the vent on the RH side that was hitting the exhaust. Fitted a boot to the cable and sealed the cable inlet. All now good. Initial set up was a 3.5 slide, 48 pilot, 125 main, JJH needle 4th clip down. This made a significant improvement in performance unleashing the potential that I felt was always there. However, off idle performance was not great. Worse that the Dellorto! Made some jetting changes to no avail. So on the advice of Paul from the Hell Team, fitted a #3 slide and a 45 pilot. The feeling was that due to the larger intake diameter the initial vacuum was not sufficient to draw fuel. The smaller cut out increases vacuum thus enabling faster fuel delivery. It was also suggested to fit a flywheel weight and to go back to the higher compression head so I made these changes also. Outcome? Perfect! The fuelling is now spot on. Equal to the FI OSSA. No lag, seamless response. The Flywheel weight has noticeably improved traction. Power is great. Hill climbs are a lot of fun! Shame the factory doesn’t deliver them with this set up? I am betting the factory models will have a Keihin when they become available. So now really, really happy with all aspects of the bike. Now to see if it improves my ability!! Thanks again to those that offered advice. Hopefully this will help others looking to unleash the performance these bikes are able to produce. 2 Quote Link to comment Share on other sites More sharing options...
telecat Posted September 18, 2014 Report Share Posted September 18, 2014 (edited) I have to say that if you buy the Kehin from Splatshop in the UK and state it is for a JGAS they will "tailor" it prior to delivery. We have stuck with the HC head as well as Chris wanted the Power it delivers. Also play with the Plug gap, slightly more gap than recommended worked really well for us. Edited September 18, 2014 by telecat Quote Link to comment Share on other sites More sharing options...
cabby Posted September 18, 2014 Report Share Posted September 18, 2014 You guys must be riding at a high level if these things are so crucial. I'm almost getting put off buying one now if they're fueling needs so much work. Quote Link to comment Share on other sites More sharing options...
jkmr1 Posted September 19, 2014 Author Report Share Posted September 19, 2014 (edited) Definitely not riding at a high level. Did I need it to be better? No. Just like things to be as good as they can be and don't mind spending the time or the money to improve things. it's a challenge! The world of aftermarket accessories and performance aids would not exist if other people did not seek the same. Plus manufacturers would not offer factory models. Pretty sure the dealers are happy to support us! Go ahead and get one if you're keen. its a great bike out of the box, just not quite perfect! (Is anything?) Thanks for the advice on the plug gap telecat. I fitted a new plug and set the gap as per the specs in the manual. Bike ran pretty rough afterwards. Fitted the old plug back in and all was good. I put it down to the new plug being faulty. What gap are you running? Do you know why the wider gap improves performance? Cheers. Edited September 19, 2014 by jkmr1 Quote Link to comment Share on other sites More sharing options...
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