OzVMX Forum
Marque Remarks => Suzuki => Topic started by: POM on February 14, 2012, 02:37:21 pm
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Trying to get this bike to have a decent bottom end is proving difficult,feels a bit like the choke is on a little bit, have dropped the needle down to its leanest position which improved it considerably,put a 30 pilot in it(was 50 standard) improved it some more (wont idle now either)far from cured it though......gets worse as it gets hotter, indicating too rich
it has a massive mid/top end...........but this low end issue is hightlighting a vicious powerband when it finally comes on song......................any suggestions?
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Try going down 1 size in the needle jet as you have no adjustment left to go leaner on the needle.
Is it the std Mikuni flatslide that came out on the 500's? they are not a very good carb and even worse when the slide is worn. Some guys have good results using a new Keihin flatslide.
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as far as i know its the standard flat slide carb...and it does have some wear on the slide...not a huge amount though.....what about a leaner needle?are they available?
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as far as i know its the standard flat slide carb...and it does have some wear on the slide...not a huge amount though.....what about a leaner needle?are they available?
Very hard to get different needles and information on the needle profiles, much easier to try a smaller needle jet. Those things run eratic and are hard to jet with a worn slide and from memory the idle isn't adjustable
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Think i might just buy a new carbie ready jetted.......any suggestions on size/model?...and a decent jet spec.........
Why this has come to a head is because after spending hrs messing with this rm and thinking id got it as good as it was goin to get......i rode a yz 465 and it ripped the rm on low end smooth power......is that a fair comparison?? how do they normally compare??....or is my rm sick......????
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Not having ridden a RM500 I can't give you a fair comparison, but I can tell you my 465 will sail past the 500's of the start line and I am not a gun rider I can tell you!
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Think i might just buy a new carbie ready jetted.......any suggestions on size/model?...and a decent jet spec.........
Why this has come to a head is because after spending hrs messing with this rm and thinking id got it as good as it was goin to get......i rode a yz 465 and it ripped the rm on low end smooth power......is that a fair comparison?? how do they normally compare??....or is my rm sick......????
A properly jetted RM500 runs strong all the way thru the revs and should have as much or more grunt than a 465... most of them came from the factory jetted way too rich.
A mate of mine has a new 38 PWK Keihin on his 500
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I have a new Mikuni flat slide on my 84 KX500 and it might be a good baseline- jetting specs as follows:
Main jet - 320
Pilot - 35
R4 needle jet
6FJ41 needle
Slide 4.0
This is very close to the stock settings apart from the needle and slide. The slides have different numbering to the old oem carbs. Hope this helps.
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Have a talk to D Project. His RM 500 seems to pull nicely everywhere. :)
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I say get rid of that yellow thing and stick to the YZ's :D. That thing doesn't handle very well either compared to the yam's and blows head gaskets at the drop of a hat ;)
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I say get rid of that yellow thing and stick to the YZ's . That thing doesn't handle very well either compared to the yam's and blows head gaskets at the drop of a hat
mmmm..... think i sorta asked for that....but anyway..even though the yellow piece of custard upsets the demeur of my wonderful "white and red ones" i will persist with it....just to anoy.. ... the lover of all things yellow ....mr d project!! ;D
i also forgot to mention i was trying to jet the rm at approx 800mts above sea level.....how much difference would this make???......
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My suggestion would be to take it to a good tuner and explain what you want and he should be able to set up the bike the way you want it or at least the best it can be. A good tuner with a Dyno and Carb Parts should be able to sort out your issues and change out what is worn and wrongly sized. The question then is how do you find someone that is good and knows two strokes. Best of luck.
Regards,
Kevin
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suck it up pom
i reckon you are just not used to riding big bores
stick to your 250 buzzboxes
P.S. or you could try the mikuni carb guys t.d. hatrick in townsville they will answer all your questions 07 4771 2677, www.mikunioz.com. The guy there sells brand new, jetted mikunis ready to bolt on and he knows EVERYTHING about these carbs
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Just stirring you up mate ;)Your bike sounded and ran great at Yanakie.
I found mine was rich as well when I first built it,but then I changed to the jetting spec to the one in the Motocross Action test from back in the day.
The article on the RM500's in VMX mag has the same spec's. May also be that pipe you are running, the DG ones are probably more suited to the lower rev range.
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P.S. or you could try the mikuni carb guys t.d. hatrick in townsville they will answer all your questions 07 4771 2677, www.mikunioz.com. The guy there sells brand new, jetted mikunis ready to bolt on and he knows EVERYTHING about these carbs
I reckon they know SFA , expensive and are a complete PITA to deal with . Ian Williams Tuning is where you can get actual answers.
POM have you thought about a plug chop? The altitude by itself not have a big effect on jetting, what it does to the air temp and pressure definatly does, which is what your suffering from. In the good old days of 2T GP racing Kyalami circuit in South Africa at 1500m required a completely different tune. Was only good for that track.
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Would the Mikuni PowerJet kit work Ok on this carb? they have the fitting already cast into them.
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johhny o is on the money you need a leaner needle jet for sure
reset needle to middle and install leaner needle jet
i would have to check what i ran in them in the past
the one i have now runs a 40mm roundslide but thats another story ;)
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Would the Mikuni PowerJet kit work Ok on this carb? they have the fitting already cast into them.
;) that would work a treat
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Update:
spent a further couple of hrs last saturday with this jetting issue.....fitted needle jet 2 sizes smaller and set the needle at middle......improvement!!.....lowered needle to lowest...more improvement but not right......with the temp at 35degs and 800mts above sea level, I sorta gave up as it seemed a pointless excercise to get a good setting at that extreme temp and altitude...... i suppose a leaner needle will be the next step.....but!!!...temp or not, the settings are now so far lean from standard its causing me concern that there might be somthing else wrong with it other than jetting........any thoughts??......and oh yeah!!.....it was starting to detonate after 10 mins of good flogging...even though its had a real nice squish and combustion chamber volume job done on it.
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Have you looked at the cylinder head, piston crown and plug? Can you post a pic? How long did you continue to ride after the deto set in?
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how is your timing ;)
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I sorta called it a day after it started to detonate...and i never got round to doin a plug check.....the timing is food for thought.....iv never checked it since i had the bike (10yrs) might have a look at that this weekend.....hopefully the weather will be cooler which should make things easyier..
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P.S. or you could try the mikuni carb guys t.d. hatrick in townsville they will answer all your questions 07 4771 2677, www.mikunioz.com. The guy there sells brand new, jetted mikunis ready to bolt on and he knows EVERYTHING about these carbs
I reckon they know SFA , expensive and are a complete PITA to deal with . Ian Williams Tuning is where you can get actual answers.
POM have you thought about a plug chop? The altitude by itself not have a big effect on jetting, what it does to the air temp and pressure definatly does, which is what your suffering from. In the good old days of 2T GP racing Kyalami circuit in South Africa at 1500m required a completely different tune. Was only good for that track.
I think Lozza must have had the same experience I had with Mikunioz when I was sorting out my Mikuni Flatslide that was on my Maico 490. They would sell you anything you asked for, but would not or could not offer any advise. On the other hand, Ian from Ian williams tuning was great to talk to, sensible logical adice and was very helpful. He even asked if I would send the carb to S.A. and he would check it out for me. I would only use Ian Williams now for Mikuni parts and accessories.
I still think it would be quicker, cheaper and less frustrating to get your bike to a good bike tuner.
Kevin
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The plug has the answers, cooler temps will lean out the mixture further
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Iv checked the plug and it looks real white....bit scary.....I must be mistaken here as i could have sworn this bike was running rich at certain throttle openings,the timing was slightly advanced..i fixed that.
After some further thought about the jetting in this bike, it came to me that i didnt realy know what the standard jetting should be...quick read of the clymer manual (im not totally convinced of the accuracy of that book) tells me the 84 was slightly different to the 83 and 82 465... it said the following
needle= 6fm......somthing or other....it had a 6fj41 in it
pilot=40....iv been trying a 30
needle jet= r4....im down to a r 0
slide should be a 2....thats cool
main should be a 300....i was at 320
So apart from the needle jet iv set it all back to standard and im going to start again.
As the weather was crap last weekend i gave testing a miss,will have another go on sat.
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Very little improvement with the stock jetting (if any).......so last weekend i tried a different carb as an experiment.....a 38mm round slide mikuni of a yz 250...jetted to rm500 spec......much improvement...low end was smooth and predictable and good strong mid range...although it seems to have lost its top end over rev a bit....and it was running real hot and eventually detonating again....bigger main jet req i reckon.....im runnin 290...
On close inspection the slide in the original flat slide carbie was sloping about somthing shocking.......which cant be right.....or can it?
All this points me in the direction of a new flat slide carb....who's the best supplier of em?..any contact details would be appreciated.
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I bought my TM38 from this guy. He has good prices on needles, jets and needle jets also.
http://www.ebay.com.au/itm/Mikuni-TM38-85-Flat-Slide-Carburetor-38mm-HP-Carb-NEW-/150684804962?pt=Motorcycles_Parts_Accessories&hash=item231583a762
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dohh!!....ebay!!!...why didnt i think of that...
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Very little improvement with the stock jetting (if any).......so last weekend i tried a different carb as an experiment.....a 38mm round slide mikuni of a yz 250...jetted to rm500 spec......much improvement...low end was smooth and predictable and good strong mid range...although it seems to have lost its top end over rev a bit....and it was running real hot and eventually detonating again....bigger main jet req i reckon.....im runnin 290...
On close inspection the slide in the original flat slide carbie was sloping about somthing shocking.......which cant be right.....or can it?
All this points me in the direction of a new flat slide carb....who's the best supplier of em?..any contact details would be appreciated.
Like I said several posts earlier, the slides wear making them hard to jet and get running properly.
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"Like I said several posts earlier, the slides wear making them hard to jet and get running properly"
No argument there!.....i might listen more carefully to the advice im asking for in future.
Anyway i will update when the new carb arrives......And I seem to be cutting it a bit fine for the first viper event at the end of april.....nothing new there i suppose.
Is everybody else's steed ready for action at monza....?
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I replaced the flat slide in my 84 KX500 and found the new ones have a different slide and needle jet series to the old OEM one. Yep it is ready for Monza !
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Stevo what carb did you put on your '84 KX500? I put a round slide on mine cos the std flatslide was shite even with a new slide...
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Hi John, I put a new TM38-85 on it to replace the original TM38. I had to try out a few different needles but it seems best with the one that comes stock with the carb 6FJ41 I think it is. Specs are further back on this thread.
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Hi John, I put a new TM38-85 on it to replace the original TM38. I had to try out a few different needles but it seems best with the one that comes stock with the carb 6FJ41 I think it is. Specs are further back on this thread.
Thanks mate
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Got the new carb last fri tm38 85 $155 delivered
jetted it as follows
main 320
needle jet r2
needle 6fj41
pilot 35
stuck it on sat arvo ready for viper practice sun,started easier,idled smoothly and felt reasonably crisp.....progress methinks.
alas sun at ravenswood the power delivery had a huge hole right in the middle of the rpm range,seemed rich so i dropped the needle all the way in(leaner).....even worse....lifted it back out 1 past middle(richer) improved......fitted r4 needle jet(richer) needle still 1 notch rich.....absolutely usless...oiled a plug in seconds......at this point bike was for sale....pis*ed off with it.....
Dropped needle all the way down again and wow!! different bike....smooth idle reasonably good mid...huge top end with no detonation....still not perfect but better than its ever been.
thanks to arno #72 for restraining me when i was about to take the hammer to it.
And this is how its going to stay for monza next week......whos' going?....
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Cool, glad you have it nearly sorted. That is the same jetting as my KX that I mentioned at the start of this thread. I will be lining up next to you at Monza ;)