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    Dnepr MT11, CB500/4 Road Race Hybrid
  • My Story
    Riding MT11s for the last 25 years

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  1. Hi Andy - I was hoping you were going to say yours were 26's or maybe 28's, 30mm Dellortos are on the big side for your engine I feel. If memory serves me correctly, the BSA M20 side valve 650's only ran on inch or inch and sixteenth Amals on a more powerful engine than the K750. You wont be able to judge what main jet size is best if you don't also know what needle profile and atomizer tube are fitted, all three work together in throttle progression, the only time the main jet alone is relevant is when the throttle is held wide open - which is seldom and brief on most road riding. The other issue with PHBH's is whether the carb body is setup for 2 or 4 stroke, which is why I asked what machine they came off. The 2 stroke body has a shrouded atomizer bush which protrudes into the choke of the carb, this creates a richer mixture entering the airstream throughout the lift of the needle from the atomizer tube - i.e. all the way from cracked open, to full throttle. I'm guessing from what you've posted so far that this may be new territory for you and unfortunately carburetors are rarely an 'open the box and bolt on' modification, unless someone has all ready done the hard work for you in establishing the appropriate combination of choke size, slide cut-out, atomizer, needle, main jet & pilot for your specific machine. However this is knowledge you can gain through trial and error, plus the cost of buying a selection of internals to test out. The 28's on my MT11 were 2 stroke bodies which I re-bushed for 4 stroke, I scrapped the slides, needles, atomizers, the main and pilot jets, and started a fresh with a base set up copied across from the Guzzi 500's which run the Dellorto 28's as stock. Over a number of months, 3 goes at main jet, 2 of pilot and 1 change of choke jet later I achieved the setup I wanted - easy starting hot or cold, excellent throttle response at any revs, more power, and about 10% gain in fuel economy as an added bonus.
  2. Yes the Dellortos can work if the bore/choke diameter is appropriate, what size are the carbs? The next issue is what internals do they have (see previous post), what did the carbs come off?
  3. Hi Andy, what size bore are your Dellortos? I run PHBH 28's on my MT11, seriously underrated carbs - I've run them on all sorts including a road race cb500/4. I should be able to make some suggestions on setup, but need to know what you've already tried re: idle jet, main jet, needle profile and atomiser. PM me if that's easier.
  4. Thanks for that, I'd guessed the source may be Oldtimer and you're right, they won't take UK orders since Brexit.
  5. For anyone following this thread, it's also running on the Soviet Steeds forum https://www.sovietsteeds.com/forums/viewtopic.php?f=5&t=58196
  6. Hi - have you read through this recent thread? viewtopic.php?f=5&t=57162&sid=400cc078e ... 51e16b7703 My four pennyworth is toward the end and my poor starting issue was resolved by junking the recently fitted Sovec module & coil, but like you, I'd spent hours playing with the carburation first. One question I do have, what coil were you running on the original points setup?
  7. Yep, the stack pipe was partially crimped over at the tip, and the weeping was being caused by scoring of the valve stem and body, bits of crap have obviously got trapped between the two at some time. I drilled the stack pipe then spun up the valve stem and lightly took some fine wet and dry cross it. I couldn't get in to dress up the valve body surface, so once the valve stem had been cleaned up, I gently lapped it in to the valve body with some fine cutting paste - 2 x 10mm nuts on the threaded end and then 10mm socket on a speed wrench. The result was a nice snug fit that really benefitted from the red rubber grease on the rebuild, the valve action is now smooth and no weeping in the off position. Thanks guys.
  8. Thanks CZ, that's the juice I've been after. Yes I'd imagine that 1:1 is stretching it in 4th and will go with 21/25. Could you tell me where you sourced your gears from?
  9. You can't go wrong with Boyer - I'm still running one on my 500/4 Honda, fitted over 30yrs ago.
  10. Hallo Chris, bitte entschuldige mein Deutsch, ich benutze Google Translate. Hier ist ein Link zu den Informationen, die Sie benötigen, aber ich fürchte, es ist auf Englisch. Freundliche Grüße. https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.russianiron.com/eafranke_ural3/Part%20V-11-%20K-68%20Carbs.pdf&ved=2ahUKEwjghqGb-qPuAhWmQkEAHZjiDJUQFjABegQIAxAJ&usg=AOvVaw2AYuwlj26_pBnGogUm2Voz
  11. Ditto - Sovek problems I fitted the latest Sovek unit (slotted cup rotor) simply to save the periodic checking/cleaning of the points, and wished I hadn't bothered. From the outset the spark was weaker than the original points with Jap coil, but other than that no issues. However over time, starting and tickover issues emerged and slowly got worse. Not suspecting a new ignition system might be the cause, I chased my tail, re-adjusting, striping and cleaning the Dellorto carbs. Finally the bike wouldn't start at all, and found there was no spark. I checked the whole system through for continuity and resistance on low and high tension circuits, and everything tested out. Finally I opened and tested the Sovek unit and the PCB had failed, and was still less than 12 months old. I'm back to points and Jap coil, fat spark and firing first kick, hot, cold, rain or shine.
  12. Thanks ND, I will see if I can overhaul rather than replace. Thanks for pointing me to the Franke archive, great resource. The main problem I'm having with this petcock is fuel weeping through to the carbs when in the off position, no matter how tight I adjust the brass valve stem. Will follow your mods, re-assemble using some red rubber grease (I've not done that before), but was also considering lapping the brass valve stem into the valve body with some fine valve grinding paste, is that something you've done or heard of before?
  13. Thanks ND - really helpful. It's the usually problem of finding alternatives to the stock petcocks which invariably weep, seize or snap due to crap metal (happened to me twice over the years).
  14. Could someone remind me of the size and pitch of thread for Dnepr petcock (MT11) fitment into the fuel tank. Thanks
  15. The Citroen part number for the centre box I believe is CIT3036. Depending on the after-market make, they can be torpedo design or 'bean can' but perform the same. The ones I have are made by EuroFlo. The up-flow end slides snuggly into the header pipe and is simply secured with an exhaust clamp & a smear of compound, the exit pipe has a mild steel fixing bracket that is easy to remove with hacksaw or angle grinder.
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