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Discussion in 'Thumpers' started by MCmad, Jul 14, 2008.
Any progress on the non-starting Dr750??
Big blue could be "done". By done I mean chassis is sorted, electrics reliable, brakes good, doesnt deink much if any oil and shes largely stociometric.
Shes running the stock carbs on stock induction but mains of 115 were required to get the afr into goldilocks territory. Power on a 250i was 40 odd horses (with a dragging rear drum) Mpg is superb. Delivery is crisp and I drilled the grp decible killer a touch as without it she made more horse right off the bottom but the mid and top suffered then. My belief being an open small volume can is a one trick pony on my bike.
Of note she will barely crack a gps verified 100 mph....which she did with ease on 120 mains but was rich everywhere else for your pleasure! This shouldnt annoy me as the only time i ever do 100 mph is to see qill she do with 100mph lol.....but it annoys me as it demonstrates an inability she shouldnt have.
In short i think we were leaning her out on the mains perhpas to account for wear somewhere in the carbs. With the setting stock bar mains and tge floats aok the only thing i can think of is emulsion tubes but the needles didnt show wear!!??
Over winter I'll chance the 36mm carbs from Marco again. I changed idle and mains back towards stock numbers as she was chocked rich on 125 iirc and i forget the idle...but i changed them to similar to stock. I think if i can dial them in (im a big amatuer here) they could be great but my dyno guy did not like the ease with which the slides could be pressed up. Said it will cause problems. In comparison the resistance of the slides to being pushed up on the stockers is about twice as great. I dunno as thats beyond my paygrade. What say you?
Big red is going good. Did 100mile trip and the only thing shes doing is a hanging idle at 1750 rpm. She has a strong spread of shove that bike! I like that there is absolutely no auditory drama with the stock can and she just gets on down the road.
Have a 3 bolt flange on the way from our Resi and both a busa and first gen gsxr 1000 stock cans on the way. Also have this
On the sacrificial alter to fit the above on red. Ill use the gpr link for blue. Blue will get the gsxr 1k and red the busa.
Now to work!
Lol that question wasnt directed at me was it? lol!!!
No it wasn't.......but good to hear from someone who's had their carbs on and off possible more than me.
The question was really for JoelBitar from Stockholm why was having the mystery non-start problem.
This is my bike exactly. I'm rather kicking myself because Derek from Motolab used to be just 70 miles or so away from me. He has the most expertise with these carbs and dealing with the KTM 640s. He would be who I would trust to put my bike on the dyno and know he'd do everything possible to get the fueling perfect without doing engine damage. He's now moved half way across the country
If the carb removal process wasn't so damn difficult, I'd probably be fiddling about even more but as it is, the best thing I did with my bike was to rebuild using new EVERYTHING O-rings, emulsion tubes, slide guides, needles etc. I think the needle/emulsion tube wear is the devil that plagues these carbs since I think the effects occur before we really "see" any significant wear.
From my Transalp/Africa Twin experience (that has the diaphragms attached to the slides as one piece) has shown me that new diaphragms are also important. On that bike (a V-twin) I simply could NOT get the carbs to be in sync both at idle and at 4000 rpm until I replaced the diaphragms with new ones. The new bits were obviously much more pliable/flexible than the old ones. Even though the old ones would function with no holes or tears, the resistance created lifting the slides seemed to increase creating the imbalance.
I'm wondering if the same isn't going on with the Suzuki carbs (and you can at least replace the diaphragm as a separate part).
The whole balance between the diaphragm, the slide spring length/preload number of coils etc still has me a bit baffled.
This is why I still lust after Stefans performance carb mod......to just connect the slides to the throttle cable and eliminate all the monkey-motion.
Glad to hear you were able to source the different silencers. It might be informative to try all of them on one bike to see what performance differences exist. The Busa can should have the most internal volume.
Let us know what you discover.
Was only reading a post of yours from ages back that popped up in a search on bst's about replacing the diaphragms. Will order four oem's payday, emuslion tubes too. Lifes too feckin short to be chaisng bst ghosts when you haven't a clean slate to start from. Especially when it's arse ache pulling and fitting carbs on her.
How much are Stephans carbs?
If somone other than us Ray is curious about my fumbling attemps to fit a suzuki oem can to a big then read on.
The dominator can arrived, seems well made, but is hilariously loud even with the db killer. Bike sounds lean, sharp and barky down low on. If i pull the choke she revs lovely and the sound softens a touch. Must clean the carbs and check whats fitted in the idle circuit.
Feel better about using just the link pipe as imo the dominator can is not a match to our bike without drastic obstruction to silence it.
Great news is the links pipe from dominator is a match for Resi's flange. It is 48.5mm and the flange centre hole is 49mm.
Plan is to orientate the flange on it so the can clears the tyre, swinger and passenger peg, mark this orientation and have it tigged with some pipe going proud into the busa can to clear the gasket.
Busa cans opening is 60mm so 11mm bigger which I'm guessing isn't great for flow but hopefully it will be grand.
Yeah busa can is bigger volume, longer and heavier. It weighs 3.1kg. The gsxr1000 k1 can weights 2.1kg. The dr650 community rate both but the gsxr can seems to be the one most want.
The busa can will i reckon fit without passing the licence plate if I slide the link pipe up the header a couple cms. One chap dynoed his dr650 which shows good results with it. The big volume is a good match for low/mid and noise reduction.
The gsxr can has a larger outlet so is better up the latter 50%
The tack welds have been broke on the retaining nuts end cap. Groaned when I saw this but everything inside is unaltered thanfully. Thread locked them back in.
You really must start with a stable foundation for exhaust/carb tuning. New slide guides. All new O-rings. New emulsion tubes and needles. You'll be shocked (depending on how worn your carb were) with the changes.
If you have trouble sourcing some things give this site a look https://store.moto-lab.com/bst33-fuel-system-parts
This GSXR / Busa can project is interesting. I currently have huge 1100cc Yamaha street bike silencer. I like the low sound and function (volume) but it's really heavy. Weights about same than SR41 original silencer!
Lol they are simply gorgeous.....but cost more than half the price of the red big!
At some point down the line I'd consider them for the blue big.
Worth looking into but always nice to shave a few kg. Also if too big it might foul tyre/swinger or peg.
Yes, the size is problem with the one i have now. I'd like to have small soft panniers as close to the bike as possible, like i did with the original silencer. So i also want to have the silencer as low as possible. At least same level as the original in sr41. Sounds like winter project again.
Aapo, if you are after pannier frames...
Well built and good value!
Hi friends. Good Morning. Some previous posts have talked about fuel pump but I still need help. I got a fuel pump that may be compatible with the DR800S (SR43). Would anyone have the 1994 DR800S fuel line diagram?
I have the diagram of the DR750, but the fuel line is different.
I imagine one of the fuel pump outlets is for the vacuum hose, but as I don't understand it, I need the diagram or help.
I have this diagram of the DR750 fuel line. In this diagram, one fuel pump inlet is the vacuum hose. This is my doubt. Where is the vacuum hose connected?
Do you have an SR43? If so, here's what I found from the service manuals. There are some minor variations if you have a Swiss or Austrian machine.
But in general, there will be a vacuum port on the carburetor. The bike will not run well or idle if this port is not either connected to the fuel pump or capped/plugged in some way. Find that.
Your vacuum pump will have a large diaphragm that is activated by the intake vacuum pulse. Find that port on your pump and connect the diaphragm port to the carb vacuum port.
Hope these help:
These diagrams are perfect. Now I will look for the carburetor vacuum outlet, because I haven't found it yet. But with these diagrams it will be much easier.
Thank you very much.
I am in the process of reassembling. I painted the fairings over the weekend. All that remains is to polish and place the personalized decals.
Nice paint. While I'm not particularly a fan of black, I do like how the stripes wiggle a bit then fade to black at the end....well done.
Post more photos.
Particularly I like the blue DR. But changing the color of the bike here in Brazil is very bureaucratic. I had painted black and yellow, but I didn't like the result. So I made this different color combination.
I´ll reassemble the bike with the new colors and post here.
Interesting that the government is concerned with the color of the machine. I have not heard of this anywhere else in the world. Some governments are concerned with mechanical modifications of the machine and have regular mechanical inspections MOT in the UK and TUV in Germany but I've never heard of them regulating color before.....very strange.
Your clutch cable looks very long. I'd be concerned about snagging this on a branch when riding off-road.
Tell us about the exhaust Antonio?