dombush Posted November 18, 2012 Report Share Posted November 18, 2012 gradually getting my new purchase the way i like it. My 07 125 has a Dellorto VHST fitted and although it runs fine, the pilot and transition is quite rich. At a whisker above idle (1500-2500 revs) it loads up a bit. Also, the fuel screw can nearly be totally wound in to get the right idle mixture. So, the question is:- do 125's need an excessively rich pilot to help pickup... or is this just poorly jetted? It has a S37 pilot at present, what are other 125 riders using in their VHST's? Dom Quote Link to comment Share on other sites More sharing options...
htrdoug Posted November 18, 2012 Report Share Posted November 18, 2012 May just be dirty,make sure the air passages from the inlet horn are clean,first spray with carb cleaner and then blast with canned air. "tip in" blubbering is due to all the inlet vacuum being applied directly to the pilot jet,drawing up a solid stream of fuel like a drinking straw. The air that comes in via the air correction or bleed passages foams the fuel a bit and help it break up to a burnable mixture. Quote Link to comment Share on other sites More sharing options...
rockyrider Posted November 18, 2012 Report Share Posted November 18, 2012 I had the same problem with mine when I first got it. The D slide carburetor seems to be high performance oriented. I would try dropping the needle, one position at a time, If that doesn't work, try lowering the main jet size. A combination of the two worked for me. Quote Link to comment Share on other sites More sharing options...
copemech Posted November 19, 2012 Report Share Posted November 19, 2012 May just be dirty,make sure the air passages from the inlet horn are clean,first spray with carb cleaner and then blast with canned air. "tip in" blubbering is due to all the inlet vacuum being applied directly to the pilot jet,drawing up a solid stream of fuel like a drinking straw. The air that comes in via the air correction or bleed passages foams the fuel a bit and help it break up to a burnable mixture. Hijack- Hey Doug, any idea what jetting / reeds are in your bike(PHBL) from Jimmy? It is loverly smooth it seemed to me. Quote Link to comment Share on other sites More sharing options...
copemech Posted November 19, 2012 Report Share Posted November 19, 2012 gradually getting my new purchase the way i like it. My 07 125 has a Dellorto VHST fitted and although it runs fine, the pilot and transition is quite rich. At a whisker above idle (1500-2500 revs) it loads up a bit. Also, the fuel screw can nearly be totally wound in to get the right idle mixture. So, the question is:- do 125's need an excessively rich pilot to help pickup... or is this just poorly jetted? It has a S37 pilot at present, what are other 125 riders using in their VHST's? Dom Not sure just how many will respond here, as it seems many dislike the carb. I would guess this is a VHST 28? Although I have not messed with them by choice, I do believe there may be some validity to your suspicion you gotta run the 125 a bit rich on the pilot to help prevent hesitation when you wick them open quickly, although some just seems normal to me, even with the 26 PHBL. That pilot being S37 is fairly large, and I would be a few points down from that on a PHBL possibly, in 33-35 range, yet you may want to inquire with Splatshop Chris, as it seems he had the VHST fairly well worked out on his big bike and can tell you more. Quote Link to comment Share on other sites More sharing options...
htrdoug Posted November 19, 2012 Report Share Posted November 19, 2012 Hijack- Hey Doug, any idea what jetting / reeds are in your bike(PHBL) from Jimmy? It is loverly smooth it seemed to me. Sorry,I don't,I will find out in the offseason but weather is far too nice around here now to go taking her apart for the winter refresh. The reason I answered above is Jimmy had this think just purring at any throttle opening yet after owning it for a few months it started taking longer to clear out each time I rode it,and just off idle it was blubbering. A quick cleanup and back to smoooooooooth again! didn't bother to take down jet numbers,eyesight has a bit of trouble reading them and don't know where my magnifying glass is.:no appropriate smilie for growing old and decripite: Quote Link to comment Share on other sites More sharing options...
copemech Posted November 20, 2012 Report Share Posted November 20, 2012 (edited) Sorry,I don't,I will find out in the offseason but weather is far too nice around here now to go taking her apart for the winter refresh. The reason I answered above is Jimmy had this think just purring at any throttle opening yet after owning it for a few months it started taking longer to clear out each time I rode it,and just off idle it was blubbering. A quick cleanup and back to smoooooooooth again! didn't bother to take down jet numbers,eyesight has a bit of trouble reading them and don't know where my magnifying glass is.:no appropriate smilie for growing old and decripite: Call him, it is easier! Ha! Don't tell him I want to know! I have heard some of them guys like Jerry Young will do some grinding to change the slide lower profile! Edited November 20, 2012 by copemech Quote Link to comment Share on other sites More sharing options...
htrdoug Posted November 20, 2012 Report Share Posted November 20, 2012 (edited) So if Jimmy knows it's you the specs will change? He's got a pipe guard for me I need to pick up and I might buy a Ti header pipe from him,sold my TY350 and thinking about buying more carbon fiber for the 250. I'll be taking a spin on Jerry Young's 2012 290 on Dec2nd as my new buddy Bill who bought it is coming down to ride that weekend,I'll see how smooth it is. Edited November 20, 2012 by htrdoug Quote Link to comment Share on other sites More sharing options...
copemech Posted November 21, 2012 Report Share Posted November 21, 2012 (edited) So if Jimmy knows it's you the specs will change? He's got a pipe guard for me I need to pick up and I might buy a Ti header pipe from him,sold my TY350 and thinking about buying more carbon fiber for the 250. I'll be taking a spin on Jerry Young's 2012 290 on Dec2nd as my new buddy Bill who bought it is coming down to ride that weekend,I'll see how smooth it is. Doug, I am allways open to suggestions! When I rode that bike back in March, it was very good to me. I don'n know if I told you , but I did recently pick up a "12 2.5, and it is still basically stock. It runs well, but not AS smooth as yours. Typacally in the past I have used the Boyesen reeds which seem to have a smoothing effect down low and made the 2.9's a bit less aggressive. On this one I have not even looked at the ignition timing, bit is does seem to chug well without stalling or kickback, so I may leave it alone. Getting back to Dom's original thread, my experience suggests these Dells, are just a bit less on the transition as compared to a Kiehin, and when you get into the range he describes, you need to back off the pilot. My best experience soo far has been to get them to lean smooth running at 2 turns out on the fuel screw(or so) with little(or no) blubber upon transition. To do that I usually need a 38 pilot for a PHBL on our fuel. Seems to me they are not the most consistant things in that range, but they generally do work. My motto is still that the Dell is the best carb that $15 will buy! I may need to up that with inflation ! Ha! Oh, BTW Doug, if Jerry had a "12 2.9 it will have the K carb unless he did something. One day I am going to do a U tube vid on this! Edited November 21, 2012 by copemech Quote Link to comment Share on other sites More sharing options...
dombush Posted November 21, 2012 Author Report Share Posted November 21, 2012 (edited) Thanks for the suggestions So, its currently running an S37, its blubbery on the transition and fuel screw was too rich until fully screwed in. Tried a U37 (because i had one) and the fuel screw was correct at around 1.5 turns out. Ever so slightly rich on transition Waiting for an s35 from splatshop (Chris told me that the relationship between S/U Dellorto pilot jets is.... S=U-3). hoping this is correct mixture at idle fuel screw 2 turns out and the transition is smooth and clean. I'll let you know (hoping for a package tomorrow) Dom Edited November 21, 2012 by dombush Quote Link to comment Share on other sites More sharing options...
dombush Posted November 23, 2012 Author Report Share Posted November 23, 2012 Excellent S35 pilot arrived last night and immediately fitted and tested in the garage. Immediately ran better and wasnt too weak when snapping the throttle open from tickover. I found that the ideal fuel screw position is sensitive on the VHST. Need to test it under load though, somewhere other than the garage!! Trouble with looking so closely at the bike for a long time is you notice other things like a slight drip from the water pump tell-tale and the gearbox breather pushing a bit of oil out when the bike is tipped over. No rest for the wicked!! Quote Link to comment Share on other sites More sharing options...
copemech Posted November 25, 2012 Report Share Posted November 25, 2012 Excellent S35 pilot arrived last night and immediately fitted and tested in the garage. Immediately ran better and wasnt too weak when snapping the throttle open from tickover. I found that the ideal fuel screw position is sensitive on the VHST. Need to test it under load though, somewhere other than the garage!! Trouble with looking so closely at the bike for a long time is you notice other things like a slight drip from the water pump tell-tale and the gearbox breather pushing a bit of oil out when the bike is tipped over. No rest for the wicked!! As the bike is a few years on now, and you prolly get the alcohol in the gas too, It does make the crank seals suspect if it is pushing oil a bit? Might try doing the test of finding you a clear tube and putting it on the vent externally to the side. Run the bike then see if it is making pressure or vacume to the tongue, or submerse in a cup of water for bubbles or suction. Quote Link to comment Share on other sites More sharing options...
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