Dave@OZ

Member
Jan 31, 2005
5
0
Hi Guys,

Not sure if anyone remembers my original post in Eric Gorr's Forward Motion but I just wanted to give you the update after my PWK39 purchase for the CR5.

Well there's more power everywhere as you'd expect but the blubbering is still there!!... just off closed throttle now (upto 1/8 only) To be fair the guys down here who sold me the Carb (which came with a 'tuned by Sudco' sticker on it btw!) have been really good and are geniuely trying to help sort it, I've had 3 different needles from them now trying to correct this, standard is DGH... and I've tried DGJ/K/L, all of which having a wider 'straight section' diameter only, so it should be effecting the A/F mixture in the right area... still no good. I'm beggining to think I'm trying to tune out a charecteristic of the CR5 engine that can't be removed! (and so is the shop). Not sure what the next step is now, thought about a bigger slide cut-away but if I'm reading Eric's article(s) right, that would affect the A/F mixture at a slight larger throttle opening than where the problem is... and at $120 per slide, I really can't afford to be guessing. Other charecteristics since the carb change... popping from the exhaust almost immediatley after the throttle is closed (at any rpm)... the bike was also quite smokey at idle on the standard 60 pilot, I changed this with the 55 from my PJ carb (which is actually 2 sizes down) just to see the difference, less smokey but it had no effect on on the problem, nor did any air screw setting from 1 to 3 turns with the 55 or 60 pilot installed... so, for want of a techinical term.... I dunno !?!?

Anyway, any thoughts on this would be appreciated.

Dave.
 
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Dave@OZ

Member
Jan 31, 2005
5
0
Thanks for the replies... yes, with each new needle I went back to the middle clip position (standard) as a starting point, then dropped it down once I saw there was little or no difference... I'm now running on the DGL needle in the leanest clip position (top groove), doesn't seem to improve the problem much, just takes away from mid-range... 48 pilot?... well I'm ready to try anything at this stage... I was under the impression that the 'popping' was a 'too lean' type of condition but maybe not... I think I have a 52 pilot somewhere left-over from trying to tune the PJ carb so I could try that and see it improves anything...
 

Dave@OZ

Member
Jan 31, 2005
5
0
Quick update... 52 is in and IT'S BETTER! :nod: Ordered a 50 and a 48 so will try them when they arrive but feeling a bit more positive about sorting this now... also put the 170 main in whilst I had the bowl off (up from 160) test ride was at night so hard to see if it's was smokey at 1/2 to full throttle but there was certainly no blubbering anywhere and... she was quick, need to find somewhere quiet so I can take a plug reading, what's the bet I end up back on the original needle also (doooh!)

Big thanks for the your advise on this one... it's helped me see the light!
 

Dave@OZ

Member
Jan 31, 2005
5
0
Hi guys,

Another update on this, I'm all the way down to a 42 pilot (yes 42!) and whilst things are MUCH better the blubbering ain't gone!... seriously worried about running too lean now and there's only 3 leaner jets for this carb from keihin!

Starting to get the 'surging' back on deceleration again... which says 'too lean'... blubbering says 'too rich' ???

very confursed... :(
 

bikepilot

Member
Nov 12, 2004
804
0
As for being too lean, I doubt any damage could occure as long as its lean only at low throttle/rpm as there is not enough heat generated at thoes conditions to worry about. You might try going back down to a 160-165 main and see if it helps. I know mains primarily affect 1/2-open throttle, but they do have some affect at lower throttle openings. Might be worth a shot. Also, be sure that your reeds are in top condition. If the problem still persists, I would suggest that you try alternate pipe/silencer/read block combinations. I have come accross situtations where all the jetting (or re-mapping) in the world wouldn't cure what seemed to be a fueling problem. Switched exhausts and the problem was gone.

I'v experenced this on a KX250 and a TL1000S. Couldn't get either to run perfectly with the stock exhaust. Tried various jetting combinations on the KX250 and it was as you describe, blubber, but going leaner hurt the power output. A FMF fatty cured it. On the TL, I had some stumbles between 3500-4500 rpm. Tried numerous maps (PCII) nothing cured it completely. Bolted on an Akro Evo Ti system, mapped it for said system and it was cured:)

good luck
 

Faded

~SPONSOR~
Jan 7, 2003
842
0
Dave@OZ said:
Starting to get the 'surging' back on deceleration again... which says 'too lean'... blubbering says 'too rich' ???
Could you describe the 'blubbering'? If you're lean on the pilot and the bike sees a large throttle transition the slow speed circuits can't compensate which can create what some might call 'blubbering' before the bike takes off. You said it was improved with the 52 pilot and now you're saying it's good with the 42 but has lean signs. Have you check for air leaks? An unmetered air leak is impossible to jet for.
 

Dave@OZ

Member
Jan 31, 2005
5
0
Hi,

The 'blubbering' is at a constant throttle position, between closed and 1/8, when I wind it on from there it's all go... this isn't as noticable off-road as you tend to crack the throttle open between turns and shut it off quickly, like I said though I ride this bike on the road also and this is where it's really noticeable!, cruising along through the traffic at say 50mph with the throttle between closed and 1/8 doing a constant speed is frustrating... you have to keep shutting and re-opening the throttle to stop it. The 'surging' is just damn dangerous when you are trying to pull up for a corner hard on the brakes (on or off-road!) being a big single the bike 'kicks' forward a few meters at a time... very disconcerting if you are cutting things fine !! (this is 4-stroking?) anyway... thinking about replacing the rear pipe next, they are unusually large and long on the CR5, I've heard this contributes to the 'doughyness' (good word!) down low... reeds are the standard items, in good condition last time I took it all apart to check them on suspicion, no air leaks that I know of (I am the paranoid type when re-assembling!) had the bike from new... always done the same thing, 4000km's on it now.

Thanks again for your help/ideas here... they are much appreciated.
 

john stu

LIFETIME SPONSOR
Jan 7, 2002
790
0
humm surging is usualy caused when running lean.......i would try going back to the 52-55 pilot put the needle in the third clip keep the 170 main and try running a bpr8es projected nose plug plug to get rid of the blubbering worth a try.
 

500 0n song

Member
Nov 18, 2006
1
0
the answer

The problem of the 1/8th throttle blubbering has more to do with reed valve sensitivity than jetting of the carb. It is an afterthought of a lot of bike owners to look at other engine/intake/exhaust components. I know the golden rule with the 2t animal is to look at the fuel settings first (much cheaper!) but to address a problem like this that may not bother a lot of owners requires some cross examination of what seems like perfectly working parts. Sorry if this scares your budget! :)
 
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