Jetting Assistance Required

[peterh]

Interesting about spark plug gap. The Australian importer has found and recommended me and others to run Champion RCJ8Y rather than the standard NGK plug as they had found this helped with a bit of the "flutter" from 1/4 to 1/2 throttle. Having one that, I agree, even after dropping the needle to 3rd from top (mid range). All runs well. Makes me think that maybe I just needed to increase the plug gap in the standard NGK. Interesting. Might have to try.

Like many of us, we like to think that getting more from the engine will improve our riding and create less dabs. And I am guilty as I fitted and rejetted my Beta Evo 125 and 200 with Boyesen reeds (both with PWK carbs) and know they made a difference to engine performance and perhaps helped my riding (or that is how I justified to my wife), but then again a more skilled rider would still ride the out of the box bike better than I am likely to do. Heck may be I might even fit Boyesen Reeds to my Jotagas - perhaps when I want to fiddle than ride, but in essence, out of the crate the bike is more than capable, and reading and viewing photos of Chris from telecast's messages makes me realise I have a long way to go with standard out of the crate bike before I should consider thinking that tweaking the bike further will make me a better rider. After all actual practice makes perfect.

[telecat]

Chris always "added" his Kehin and Ohlins to his previous Marques 125's and the 250 and 300 we had. They just "tune" it to his riding style. To be frank He looks pretty good on any bike he rides to me but he will then tell you what the bike is like compared to his "ideal".

He finds Beta's a bit "dead" suspension wise although the engine is quite good.

The Sherco engine is OK but the bike is too light at the front. Too many seem to have been "slowed" which he does not like.

Gas Gas he thinks have moved away from the "chuckable" bikes that were about to 2011 and the engine has not gone anywhere for a while.

The OSSA engine is too linear, he prefers the engine to generate torque faster and the front end seems too low and heavy.

We went JTG because he liked the handling and the engine in 300 form has a lot of torque. He does ride off the bottom end and likes a low idle so most of the work on the Kehin was to make sure it did that correctly and cleanly went straight up the revs. He Prefers Stop Trials and the Bike is setup for this although the same setup works pretty well in the few No Stop he does.

Basically Most bikes are 90% there for the way you ride. Tweaking just matches them a bit closer to your riding.

[peterh]

So if staying with the standard Dellorto PHBL26 on a 2014 JT250 and if putting Boyesen Dual Stage Reeds in, what jets and needle settings might be suggested.

[gasgas249uk]

why change ?

[telecat]

Chris has added some Boysen Reeds but the carb has not needed any tweaking. I would just install them. The Point on his was to increase the speed of pickup which it has done. Listening to it the noise it makes as it "hits" peak revs is very similar to that of "works" bikes when they do the same.

Edited December 3, 2014 by telecat

[peterh]

Thanks telecat. Did you add boyesen before or after putting th keihin PWK on? I am thinking that with the dellorto that I should be able to leave slow jet alone and adjust the fuel mix at idle easily by the fuel mix screw given that normal is about 3 turns out, so by less turns will be able to compensate for the usual increased richness when running with the dual stage boyesens. I have previously put boyesens in my Beta Evos to good effect, but had to change jehtts to optimise it. Your experience is what I would like to achieve in just making the bottom end a little crisper, which is what Steve Saunders also said was the effect. Thanks.

[telecat]

We did it about a month ago and the Kehin has been on since January.

[ajharry]

I was the proud owner of a 2014 JTG 280cc, best looking bike I've had I think.

Agree with the post above and advise from Paul Arnott - Hell team. To add, your spacer engine side of the reed block will also make this flow WORSE, emphasising the already worser flow rates of the larger kehin carb. Anyone that thinks these k carbs perform better down low must have had the dellorto performing not at it's best.

I"ve never been concerned with the fuel I ran in my last 15 or so trials bikes, until this JTG, certainly did not like 98 shell... fouled plug every 20mins, jetting seemed perfect till ''it went'. E100 United sorted this. E100 a slightly leaner fuel so had to go back to std or richer jets.

Glad you've got it sorted, often pays to ring the importers, they all want their brand of bikes running the best, not good marketing for any of their bikes to be running like ****... Selling different heads might be, temporarily. On heads, I had both std and super high comp on mine, squat difference to jetting.

Glad you got it sorted, mine certainly sounded sweet with std carby, didn't change the plug for 1 and half years once had it sorted.

happy days

[peterh]

As an update. I did fit Boyesen Dual Stage Reeds to my 2014 JT250 with the Dellorto carb. It has made the bottom end slightly crisper and seems smoother all the way through rev range. Very slight adjustment to mixture screw to adjust low idle. After an hour or so of fiddly turns, steps, double blips etc etc the plug centre was pretty good with centre electrode still darker coffee colour and a plug chop at full throttle shows a lovely coffee colour - using Champion RCJ8Y plug 0.8mm gap. I had previously lowered the needle by one step which had already decreased a bit of flutter through quarter throttle. So very happy with outcome and no fiddling with different jet sizes, needles etc.