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Discussion in 'Thumpers' started by MCmad, Jul 14, 2008.
Hi, I just sprayed my engine satin black. That's what I did this afternoon.
Yes, I am about to change the bearings and I think the top one is metal and can be reused. Rob
Hello Gents,about 18 months ago I was fortunate enough to buy this beauty.
As you can see the tanks, and plastics are in very good condition.
Since then I have given it a good clean and have painted a few parts in order to tidy them up and now it is going back together again.
Which brings me to a problem that I have had with the bike. Ever since I got it it has always leaked fuel from the carbs.
Soooo, I took the carbs off to have a look at them. Now, I'm sure that you will be able to spot that the carb that was giving me the trouble is missing something quite important - like the main jet:huh WTF?
And, upon further investigation found that something else was missing. I don't know what it is called so I'll show you what it is. It's this little brass tube (jet?) that my screwdriver is pointing at.
Now, I'm no factory trained mechanic but I'm guessing that these missing parts may be the reason why fuel is pissing out of my bike!
So, my question is what is that missing part called and where can I get one from? Also, I guess that I should be able to order a main jet from a Suzuki dealer or from Stefan Hessler?
Any help is much appreciated, thanks
Very nice bike.
So, to be terse, on to the questions.
The main jet is, indeed missing. Are you certain it wasn't in the bottom of the float bowl when you took the bowl off?
If you were not the one to replace the phillips screws with allens, then whoever was there before you seems to at least have some inkling of doing things correctly, so it's quite odd that the main would be AWOL.
Of course, the main should be replaced. If the UK is anything like the USA, the jets should be available at almost any dealer. Make certain to get the correct size. It should match the other main in number.
On the tiny brass tube, the SR41s (750s) only had a "choke" (enrichener circuit) in the left carb. Unless I'm mistaken this tube provides the fuel pickup for that circuit. The same spot in the right carb should be blanked out and not drilled for anything, correct?
Now, for the fuel leak. Unfortunately, the answer to your leakage question is "None of the above"
Fuel is leaking because one or more of the small O-rings that these carbs use is dried out/cracked/torn/square in cross section/or otherwise damaged.
You'll find these O-rings
(a) under the brass tube that holds the float valve
(b) on the plastic "tree" that supports the floats themselves
(c) on the bottom of the grey plastic throttle slide guides where the guides go into the carb body.
And the other place may be the float valves themselves. If the small black taper is dented or damaged, fuel will overflow since the floats will not stop it. From here it usually fills the crankcase...which it much worse than leaking out of the carbs.
There are also O-rings on the tiny idle mixture screws down at the bottom...they are very very small but should be replaced.
Replacing all these bits is not expensive but is a bit tedious. The bits for the grey plastic slide guides I was able to find from BMW or KTM since a few of their bikes use the same parts. The Suzuki parts diagram does not even list the slides or the O-rings as a seperate part.
Setting the float level correctly and replacing all the O-ring should solve your fuel leakage problems.
BUT...you may also want to check the fuel "T" that lives between the float bowls. There is a seal on each side of this "T". If the "T" spins around in the space between the bowls with little to no effort, these seals should be replaced. The "T" should be able to rotate but should have significant "drag" when moving it. If it seems loose, fuel will leak from that part also.
Once all these problems are solved (a bit of what's required in owning a 20 year old machine) the carbs work quite well.
Lots of information and photos if you do a search for "carbs" on this thread.
Remember to use the fuel valve on the tank and turn the fuel OFF after you put the bike away for the day. Leaving this valve on is asking for problems.
GSX750 (1999) Suzuki part number 51644-12C00 should do the job.
The only difference is that this seal will sit below the lower ring, you have to mount the seal before (!) the lower ring comes onto the stem.
I did some more research on pistons.
OEM pistons with valve cutouts are not sold any more. They are superceded by simple flat top pistons without any recess or cutout.
I dug out the box of the 0.5mm oversize piston set I ordered 2 or 3 years ago for my SR42. The part number is 12100-31D00-050. And the same piston set is sold now by CMSNL for SR41, SR42 and SR43.
Conclusion - flat top piston without valve cutouts will work on all DR Bigs be it SR41, SR42 or SR43.
Thanks to BigBob on drbig.info who led to the right tracks.
Thank you very much for your reply.
Got proper cert for the exhausts to clear inspection in Singapore?
If have I buy.
Sounds like you have all the usual suspects already corrected.
The O-rings on the bottom of the slide guides will not normally be responsible for a lot of fuel leakage. But they do affect the carbs performance a bit.
The guides were designed as the "soft-part" in the carb that takes all the wear from the slides vibrating in and out on intake cycles from the big cylinder. They can have significant wear and cause problems with the fueling if badly worn.
To remove the slide, the needle jet (long brass tube) must be removed first.
They can be a bit stubborn so what I do it this:
Unscrew the main jet about 1 1/2 to 2 turns.
Tap the main jet toward the top of the carb with a small soft hammer or even the plastic end of a screwdriver.
This should start the guide moving upward toward the diaphragm area.
If more "persuasion" is necessary you can GENTLY thread in a 4mm screw (I think this is the correct size) that has longer threads and give it a few more taps. Careful here because I don't believe the M4 screw has exactly the same threads as the main jet and you do not want to "rethread" the brass needle jet.
If your slides require replacement, I was able to get mine from a BMW dealer. They are the same ones used on the early model BMW Funduro 650. BMW has these listed as a part number (slide and O-ring" while Suzuki makes no mention of this.
The last thing I'd recommend is to find the carb vent tube that exits the between the two carbs and is usually routed back under the seat somewhere near the airbox.
If you ride off-road or dusty conditions, a small air filter (K&N has them) clamped onto this line will prevent dirt from entering the area under the diaphragms of the carbs. Maybe you found dirt there while cleaning?
Also, On reassembly, particularly in cold weather, I'd recommend removing the bolts holding the airbox/rear fender to the frame. This will allow you to move these bits upward and back a few cm. This will give you more space to refit the carbs and make CERTAIN the boot between the carbs and the airbox is sealed correctly on the carb mouths.
Doing this seems like it takes longer but, in fact, will save time and bad language while wrestling the carbs back into place, pinching and tearing the airbox boot etc.
Lastly, make sure the carb vent tube and vacuum line (the one driving the fuel pump) are connected to the carbs BEFORE you install the carbs on the bike. There is very little space available for installing these lines after the carbs are in place.
Thank you Lars. Really appreciate this. Rob
Stuck my center stand on ebay and sold it but the winner decided not to pay so i have had to relist it .It"s quite heavy to post so would prefer UK or Europe . You can make me an offer on it if interested.
NOW SOLD THANKS
So tell me again just how ridiculous the shipping(cheapest option) is to Canada T3E 6A5 as it still might be cheaper than a welder
Shipping is coming back £60 /£70 .far to expensive although my sister is visiting from Toronto in July , if i still have it i will send it back on the plane with her
No proper cert for the exhausts to clear inspection in Singapore.
The devil exhaust is street legal and it came along with my drbig 750. i prefer the devil exhaust compare to laser exhaust but did the switch due to certification issues.
The laser exhaust modification done by AJ will not clear inspection in Singapore. Modification inspired by the KTM.
I have just spent several hours on the carbs and one is still pissing fuel out
I went right back to square one and stripped them down, removed all of the O-rings and gave them a good clean, wash and dry. Dried everything and gave them a thorough blow through with compressed air. As I already mentioned I have replaced all of the O-rings and lightly lubricated them as I put the carbs back together. I set the float heights using a digital vernier calliper to get them as accurate as I could.
I stood the carbs on my bench and connected up my remote fuel tank, switch on the fuel and within a few seconds fuel starts to run out of the right hand carb. The fuel seems to come from this small hole.
I opened up the float bowl on the leaking carb and bent the float valve arm so that it was virtually closed even when upside down and them tried again - you guessed it! - still fuel leaking out so, how is the fuel getting into and overfilling the float bowl if the float valve is shut?
Any help will be much appreciated - I'm starting to love my fuel injected bikes more and more!
I have one of those on the right and the one on left in my garage is an 1150 gs
Something is amiss either with the float valve
With the O-ring sealing the float valve body into the carb.
How about leaving the float bowl off. Connecting to static fuel supply and moving the floats up and down manually. I know this is a pain due to the platic non-attached to anything float "tree" that is provided on these carbs.
Hopefully this way you can see where the problem lies.
Please remember to remove or turn off ALL ignition sources when doing this.
Don't want to burn down the shop.
Remember your FI bikes are new....I can only guess what those systems will look like in 2033. At that point, I'd guess you'd be wishing for simple ole carbs.
I've been lusting after a S10 for a while now....How do you like it?
Glad to see it found a home I have found a local welder who going to try and adapt a stand from another bike for it. Thanks for the reply. Cheers Brian
Just checking in .....
Yes Tim F.I. rules, but keep working on the carbs, you'll get them sorted eventually. Nice Tens b.t.w.
I think that the fuel was still coming out of the right carb because the left was also over filling and the fuel was being transferred from one to the other through the breather hose. I took the float bowls off as suggested by Ladder106 and held the tree on using a large elastic band. I used the old float valve bodies and soldered up the hole in each of them, fitted them to the carbs and - no fuel. Fitted the new float valve bodies and put a finger over each of them and again, when I switched on the fuel - no fuel. Took a finger off and fuel flowed (under quite a surprising amount of pressure). It was then that I noticed that the new float valves and their bodies were a slightly different length to the (what I guess were OE) old ones that I had replaced. I therefore added 2mm to the float height and tested again - dry carbs
I have now refitted the carbs and have run the bike on the bench and everything is good and dry.
Thanks very much Ladder106 for talking me though this - it's great to have someone to be able to bounce stuff off rather than just sitting in the cave not really knowing what to try next