DR750 & DR800 owners thread

Discussion in 'Thumpers' started by MCmad, Jul 14, 2008.

  1. Ladder106

    Ladder106 It's a short cut, really

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    You certainly put in a respectable amount of time on this, Tim....well done.

    I've learned something also and will not assume all valve bodies are the same.

    Throwing ideas around or simply venting your frustrations are part of what this internet thread thing is all about.

    It's always easy to give advice when you're thousands of miles away and not having to do the actual work yourself, but I'm happy to be of some assistance.


    ......Now about that S10??? and, feel free to add comments about the 660. We don't get that bike in the US but I've always liked it.
  2. Longdude

    Longdude Tall Geezer !

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    Carbs are good, I'll be freaking about mine soon enough...................but look at my wheel rims, powder coated in a rather fetching, in your face red.

    [​IMG][/IMG]
  3. Tim

    Tim Long timer

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    Nice!

    Would that be by any chance a Marlboro red? :deal
  4. Longdude

    Longdude Tall Geezer !

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    Mmm, how did you guess.:clap. Lol.
  5. Ladder106

    Ladder106 It's a short cut, really

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    IT RUNS.

    The SR43 engine fit right into the SR41 frame.

    Carbs/airbox, everything fit with no problems.

    I used the flywheel, stator, and ignition coil from the SR41 engine. This all bolted up inside the left case from the SR43.

    A small adjustment had to be made for the decompressor linkage in the cylinder head. The SR41 uses the manual decompressor and the internal part of the shaft is shaped just a bit differently from the automatic decompressor on the SR43.


    The 43 uses a shorter shaft with a smaller weaker spring.

    When I tried to start the bike, the decompressor (once activated manually) would not reset and allow the valve to close.

    I transplanted all the parts from the 41 engine into the 43 cylinder head (everything fit without difficulty)

    The cylinder head of the 43 had no hole tapped to support the cable holder bracket from the 41. The head for the 43 still has a large boss cast into it so it was a simple matter to drill and tap a hole to support the cable bracket.

    Once this was all finished, the bike started easily and settled into a nice even idle.

    Whew....after a weeks work, I was relieved and excited.

    Tomorrow I'll finish routing some wiring, attach the bodywork and go for a ride.

    ........Next, the rebuild starts on the SR41 engine.
  6. mait

    mait Been here awhile

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    Good news, Ladder106!
    Although SR41-42-43 engines look similar there are a lot of small differences. Thanks for recording this info here so it is available for everybody.

    I just disassembled the carbs in order to clean and rejet them.
    The pilot jets I took out were 40, main jets 117.5 and needle in the 3rd notch.
    Everything like in Suzuki specs of SR42.
    I will install 130mains and 45 pilots now because I've changed the whole exhaust from header to muffler and probably will modify the intake, too.
  7. robmoto

    robmoto Long timer

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    Ray I carn,t wait for the outcome report.:ear.
  8. Ladder106

    Ladder106 It's a short cut, really

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    Mait,

    Rob says that the SR42 (800 engine with the older 750 style airbox) should run just fine with 125 main jets. Even with a more open exhaust.

    I dropped my needles back down the the middle position but, being a bit conservative (and not wanting to make too many changes at once) have kept the mains at 130. This is using the standard SR41/750 airbox but with a GSXR 1000 silencer.

    Rob,

    Thanks for all your advice (and everyone else' too)

    Yesterday I started the bike with tank off using a remote fuel source. Standing over the 800 engine without any body work on, I noticed at once that this engine was MUCH quieter in the top end than my old 750 engine. Overall the engine seems much tighter (it was at 37,000 k. when purchased).

    The bike started right up once I got the decomp problem solved.

    I noticed that the decomp. shaft that goes into the cylinder head is different for the manual (SR41/42) system than the shaft for the "automatic" (SR43) system.

    I should have take photos but was in the middle of my S. Holmes diagnostic state tempered with abject fear that I'd done something mental and ruined a weeks work....so no photos.

    Anyway....both shafts have a flat spot ground into the shaft at about the 9 o'clock position when looking straight at the engine from the right side.

    BUT

    The SR41 shaft has an additional flat spot that the SR43 shaft does not possess.

    This, plus the fact that the 43 shaft did not protrude far enough to play nice with the manual cable from the 41 led me to believe that I could just swap all the pieces.

    Everything fit together and the bike started on the next try.

    The tank went back on yesterday evening.

    The seat, bodywork and crashbars will be mounted today and I should have a ride sometime this afternoon.

    I'll see if I find any differences between the 750 and 800 engine. But to be fair, I think my 750 engine is a bit tired.
  9. motolab

    motolab Long timer

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    I thought you were talking about the slide guides rather than the slides.

    Regards,

    Derek
  10. motolab

    motolab Long timer

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    The rubber tip of the float needle should be inspected under magnification. It should perfectly conical, with no witness line evident where it was contacting the seat. If any evidence is visible, or if there is a gap between the bottom edge of the rubber tip and the aluminum portion of the needle, if the plunger is stuck, or if the plunger return spring is sacked out, the needle should be replaced.

    The float height should be set to 14.6mm with a float height setting tool.

    Regards,

    Derek
  11. Ladder106

    Ladder106 It's a short cut, really

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    Derek,

    Thanks for keeping an eye on this thread.

    It's always nice to hear from a pro.

    I have a good friend in Apton. I'll have to make a point to drop by your place sometime since it's pretty much on my way there.

    Appt. only?
  12. motolab

    motolab Long timer

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    Hello Sir,

    You were doing a pretty good job without me! And it is good to know that I'm not just annoying the heck out of folks...

    Just let me know when you are coming. Lunch one day maybe?

    D.
  13. Ladder106

    Ladder106 It's a short cut, really

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    Lunch sounds great.

    I meant Aptos not Apton.

    I'll call first.
  14. Ladder106

    Ladder106 It's a short cut, really

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    Well.....

    It runs.

    Everything works

    Nothing leaks

    Nothing fell off

    I put in about 40 miles this afternoon. It's good to be back on the big bike again.

    BUT

    Rob was right. It's running rich.

    Rob, the 800 seemed not really much different than the 750. Likely the fueling being off is affecting this a bit but my "Butt Dyno" didn't detect much change. It seems to pull a little stronger in 4th and 5th but is pretty rich on top .

    It pulls nicely up to about 6000 in top gear then doesn't want to do any more. When I got back the end of the pipe was coated with a nice, dry, fluffy BLACK.

    No oil, not wet (thank goodness) but veryvery black. Wipe it off with your finger and blow most of it off.

    So, I guess tomorrow the carbs come back out and 125 mains go in.

    Carole reminded me that I LIKE taking motorcycles apart. I needed that cause I didn't want to do it all again but I have to do it right.

    More later.
  15. robmoto

    robmoto Long timer

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    Ray good to see its a goer, after changing the jets tomorrow if still not much difference open up the end of the can to at least 35/38mm or in your imperial talk 1 1/2 inches through the baffle so you carn,t find it ever again and put in one of lars,s mesh inserts that he makes for pro duo mufflers but they allso after looking tonight at mine that I am now fitting to the blue bike that GPR oval muffler I believe you have one too it looks like the mesh insert will go straight in, there, 1 inch or 25mm hole just aint big enough it slowed my now 800 yellow bike down.
    Or just take the baffle out and go for a small ride with ear plugs and see what happens , you may gain that bottom end and mid range power where we ride most of the time.
    Just for a tempory thing you could get some mesh stuff and snip and fold it arround the end of the tail pipe of the muffler and hold it with a radiator clamp to give it a tad of back preasure and keeps the cop.s away while testing :D.
  16. robmoto

    robmoto Long timer

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    RAY is your fuel called E 10 I believe its octane rating about 93 I never use it but run all my bikes on 98 just thought I would mention it I have never tried the what we call the standard petrol unleaded 91 octane because it starts to go off after 4 weeks I am told and some of my bikes sit for months so no good for me.
  17. Ladder106

    Ladder106 It's a short cut, really

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    Morning Rob,

    Thanks for the tips. Thinking about it last night, I believe I'll see if I can try different exhausts first. I have a Laser (from the DR800) and still have the GPR. I thought I'd pull the "quite" inserts out of one or both of those and give the bike a run. It may be that my GSXR pipe is a bit restrictive. The only problem is that the GSXR can is the only one that I can make "US Forrestry Approved" with the addition of a mesh spark arrestor...the other pipes are street only. Runing this bike in the wild without the arrestore nets you very large (in the order of $1500) fines from our Rangers.....and rightly so. You guys down in Oz know all about wildland fires.



    Changing the pipe should also confirm that I am, in fact, running rich....but the black at the end of the pipe is a pretty good indication.

    If nothing else, this does show me that the airbox on the SR41 is truly restrictive. I keep putting off carving mine up but it seems inevitable.




    Our mandated Repulic of Kaleeforneea fuel is called "E10"

    It's 10% ethanol....if you're lucky. Some of the cut-rate stations have been known to pump more corn squeeze than the name brands.

    I tend to stick with Shell or Chevron but the highest grade fuel we can get is 91 octane (measured ROM).

    I also use Startron enzyme treatment to try to damp down the effect (collecting water for one) of the alcohol.

    I think it's a misguided attempt by all the treehugger (who for some reason tend to drive SUVs) to save the earth. Our government just sees a way to subsidize all the corn farmers in the midwest.

    Anyway...it's rubbish. A few months ago the tree hugger lobby in league with the air quality nazis cooked up a plan to go with 15% ethanol....until all the major auto builders told them they be rebuilding their SUVs after 10 thousand miles.

    In the real world, I don't know how this affects jet numbers and is one of the reasons why I try not to recommend jetting to guys overseas.
  18. Ladder106

    Ladder106 It's a short cut, really

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    So my shop didn't have 125 main jets.

    But...I have a pair of 120 and one (1) 127.5.

    So since 125 X2 is 250

    and

    120 plus 127.5 is 247.5.......

    .....I'm going to try putting different main jets in the carbs.

    They don't differ that much and with my understanding of physics there should not be that much of a flow difference between the two carbs.

    Both carbs go to the same place....so I'll give it a go.

    I also discovered that the float bowls can be dropped by removing the exhaust system and working from the bottom.

    You have to use a few "creative" screwdrivers and it helps to have allen bolts holding the float bowl on....but it's much easier than carb removal....particularly when you've spent 2 hours making certain they are attached correctly.

    So....opinions or idea about running different size main jets.

    I'll post results.
  19. robmoto

    robmoto Long timer

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    Ray one side of your piston will be rich and the other side lean your piston may split down the middle :lol3.
    personaly I would get the right ones, using 91 compared to 98 meens your bike will be a fraction leaner .
    try taking the snorkle out and or open up the side of the air cleaner by cutting it a triangle shape might help you too.
  20. Ladder106

    Ladder106 It's a short cut, really

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    Yeah, I'll get the correct jets. Just want to try it like this for interests sake.

    If patience is a virtue, then, maybe impatience leads to invention.

    I was so excited that I could actually take the float bowls off from the bottom without removing the entire carb that I figured I'd just put these jets in and ride back to the shop tomorrow for the correct ones.

    I'm sure there's enough turbulence in a 4 valve head to mix the gasses up to compensate for any slight difference the jets would cause and I'd expect the net result to be pretty close to running 2 125 mains. Plus I think I'll get one of those overbore pistons from Mait to have on hand...if mind cracks down the middle.

    I've thought about opening the side airbox but most say that doing this makes the bike sensitive to cross winds leg position etc. I have an old filter that's not too dirty so may try it there first.