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604 DS dellorto phm 40 accel pump and jetting; 604 DS dellorto phm 40 accel pump and jetting
Topic Started: Apr 6 2018, 05:57 PM (127 Views)
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Hello, Everyone

I brought a 604 DS (rotax) to give it a bit of TLC which had a badly welded r30 front pipe (Joins at rear of engine) and some carbon fibre end can (looks like off an R6?) i couldn't save the front of the pipe so untill i can fund welding up the r30 front pipe i have put on the standard thinner dia front pipe (which joins at the front of the engine) and race ccm remus end can (without baffle :dirtbike: ) with the Dellorto PHM 40 (no Accel pump)
first start was ok choke on seems rather rich with restricted air flow untill reved so slight throttle required and idle (off choke) also seems restricted air flow, first ride and she pulls well...... up to 3/4 and full throttle was flooding so i swapped out the 205 main jet :chin: for a 185 and now still pulls well and full throttle runs spot on but 3/4 still bogs n then pops and bangs and flames when throttle off off but runs better with the choke on at 3/4 throttle so i assume needles rich,

The link i used is...

so my set up atm is

Dellorto PHM40 (No accelerator Pump)
k35 Main Needle 2nd clip from pointy end :)
185 main jet
268DR Main Atomiser
CCM surge washer (with holes and cut out for air jet)
300 Float set to 18mm (as it says 17.5-18.5 in manual but will try 17mm)
B40 Idle Atomiser
32 Idle Jet
55 Starting jet/choke jet

clean light brown centre with slight black outer ring NGK Iridium plug (have ordered new brisk plug aswell)
no compression tester but compression seems good (untill decomp used) so i assume timing is also good, i will adjust tappets to 4tho in and 6tho ex at TDC to check the cam belt i installed :/

Right so i am going to follow Montys recommendations which is...

Gasket set: 52544-77
Needle: K32
Needle jet/atomiser: 268DR
Float needle valve: for the 604 is a 300.
Main jet: 175 standard for 604, 185 for a 636? Fit 185 for aftermarket cans on a 604.
Idle/Pilot jet: The CCM factory said that they fitted a 32 idle jet purely to get it through emissions, but to get the thing to run right it needs a 40 idle jet.
Choke jet: If it is a 60 put a 47 in. It will start and idle on choke then whilst you put your gear on etc., something they never do standard.
Settings on the Rotax carb are absolutely critical especially the float height which should be 17mm.
Put the aftermarket can on, up jet to 185 main and drill the airbox, try needle second richest, one groove up from the pointy end, set idle mix 1.5 - 2.5 turns out
On a 40 pilot 2.5 turns out should be enough, but if 3.5 works then itís all good!
Be sure that the slide is sitting home (closed) with slack in the cable before adjusting the idle speed.
If the slide is raised on the cable to achieve tickover the idle circuit is bypassed, this will make it a pig to start and you will never get the idle mixture correct.
Worth checking the throttle cable for free play when the idle screw is wound all the way out.
1. Set idle slightly high (so it wonít stall, with bike fully warmed up)
2. Wind mixture screw in till engine starts to hunt/ go fluffy
3. Wind screw out, counting the half turns as you go, till engine again starts to hunt/go fluffy.
4. Set the screw half way, i.e. if you counted 3 complete turns out (between fluffy in and fluffy out) screw in 1Ĺ turns, that then will be your optimum setting for the mixture screw.

.....so i will buy....
k32 Main needle (leaner taper)
new 300 float (dont know if the rubber has perished)
40 Idle Jet (worth trying any more? would the B40 atomizer restrict it?)
they do not do a 47 choke jet on dellorto? they do 45 and 40? if i go lower size does that go leaner with the mix if so i may try 45 and go from there?
but my main question which i cant find any info on is the accelerator pump, mine currently does not have one and is blanked over but i think i found them... :hug: (link below) and was wondering if it is worth drilling and tapping and installing the accel pump like the race carbs for 400 quid :chin: if so any one done it yet is it better??? and what jets/atomizers are best or is it one size? so any help is good help regarding extra possible jet/needle sizes to try or even ways for me to check what spec this bike is (besides my seat dyno :dirtbike: ), is there a way to check from the cylinder if its a 604cc or any ways to tell if the cam has been modded, above sprocket says 640707 (where is the engine number on these bikes?).


Thank you everyone :poke: :worthy: :dirtbike:
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Charlie Big Banana's
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I'll make things simple, fit a 175 main jet, 185's only for race can and open airbox.

I dont think you can fit a accelerator pump to a non pumped carb, internal drillings are not there nor the correct slide,
If it aint sharp I can play with it
My Utube Channel, lots of bike vids here. Subscribe if you likehttp://www.youtube.com/user/choppermark?feature=watch

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finally had a bit o time to tick off some jobs on the ccm604... so to pick up where I left off... I already have got a 185 main jet in with the ccm race remus end can (off road use only) and standard front pipes with a open air box. also wasn't too sure if I could just buy a heavy slide off delloroto.com and drill from the float bowl up into the accell pump? but it seems it has an internal bend and maby not accessable from accel pump or float bowl, but I cant find any internal layouts of the carb online.

so my current set up is

60 idle jet (short type) (mixture screw 1/2 turn out so I think its slightly rich)
B40 idle atomiser
50 choke (idles at 2k on choke)
k32 needle 4th clip (closest to pointy end) with shim washer underneath needle to heighten the needle more than max and make it richer
185 main jet
17mm float bowl height and also done the "blow in the petrol pipe" test and the float needle holds pressure very well

I have fixed the bogging and hanging idle now (40 and 50 air pilot jets still hung on idle when throttle was blipped, 60 runs the best)

so in my seat dyno...

she starts and idles fine (even without choke when warm), I have instant power the first 2mm of throttle, then a slight hesitation up to 4mm of throttle then from 1/4 throttle to full throttle has instant power again.
when I power on through the dead spot with choke she runs much better on dead spot also when I slow rev thru the rpm she runs much better with no hesitation, so I assume she is lean atm even on lowest (richest) setting on the main needle.

ive also checked the spark, done the tappets to 4tho in and 6tho out, cam belt is aligned correctly, no air leaks carb side or even exhaust side and carb is not hitting shock or frame and all filters are clean (even ran some redex thru it with high octane fuel from shell)..... any ideas anybody?
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To anybody that may have the same problem it seems my carb does infact have an air leak, i found out when i set my engine to TDC, remove a little fuel from carb float bowl with the drain screw, then tightened it back, tie knots in my carb breather pipes and blew down the fuel line to find the little hole on the right hand side of the idle screw and just below the choke to be pouring out of fuel?? and a slight hiss from the slotted dowel that aligns the main slide which seemed looseish (just below the dellorto writing) i have since stripped it down and found out that the hole near the idle screw is linked somehow with my choke circuit (i assume it is an internal crack as light does not show) i have recently blocked the hole and started with the 40 idle again, but it hung on idle when throttle was blipped slightly and have since found the 50 to be too rich as it runs best 1/2 turn out on the mixture screw so a 50 is too big, also dropped the main k32 needle to 3rd clip with washer underneath seems the best atm and besides a slight hesistation and bog at 2mm throttle runs perfectly through out the rest of the rev range with alot more torque, but ill order a 45 idle jet and go from there with my seat dyno... thats hoping my repairs will last... may start saving incase i need that 300 quid race carb after all :tomatoes: :flowers:... unless any body has an old carb body they would like to part with for a bribe? :poke: :arms: :angel:
But best of all... my mpg is now ALOT better :dirtbike:
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