MT-11 Blowing Air instead of exhaust.
Posted 15 March 2015 - 01:16 PM
Posted 15 March 2015 - 04:02 PM
2008 Dnepr mt 16 true year any body's guess
There is more to life than increasing its speed
__ Mahatma Gandhi ___
if only the mt 16 could go 50 mph
I think a good name for my MT 16 is (the bad girl) every body wants to ride her but nobody wants to take her home )
1980 Harley Davidson wide glide work in process to restore
2004 Harley sportster
2002 Honda A.C.E.
2014 Indian Chieftain
2013 Honda BIG RED
Posted 15 March 2015 - 05:16 PM
Best to start at the beginning and work logically
How familiar are you with Dnepr's and what are your mechanical skills. How we pitch the advice depends on your answers.
Posted 15 March 2015 - 11:57 PM
Posted 04 April 2015 - 08:11 AM
Posted 04 April 2015 - 11:43 AM
Posted 05 April 2015 - 09:17 AM
Posted 05 April 2015 - 11:18 AM
Posted 10 April 2015 - 08:58 AM
Posted 12 April 2015 - 05:41 AM
First two photos below show what such a flange (third picture) can do to the sealing surface of the cylinder and gasket if it doesn't clear the fins properly and forces the head to be tightened at an angle relative to the cylinder. Note the wide spiral-like dent in both surfaces. That caused a loss of compression. Fourth picture is the piston working in such an environment. Loss of compression and running below optimal temps result in impressive carbon build-ups. Still ran though, I had no idea about the issue until I took the cylinder apart to replace the gasket underneath it. :)
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Or it may have a simpler cause. One nice summer night I was merrily ploughing down the motorway at an incredible 100 km/h when I noticed that the right-hand cylinder would cut off if I let the revs drop below WFO. I stopped to inspect the issue after I decided that enough was enough. It turned out that I hadn't properly fastened the carburetor to its head on that side and it had almost fallen off. :) One heck of an air leak!
Do pardon if the following suggestions are old news or if they come off as pretentious.
Valves - check for leaks
Are you sure your valves don't leak at the seats? A simple leakdown check you can perform with the head out involves pouring some gasoline through the intake and exhaust ports. One at a time, to avoid drenching yourself in petroleum products. Hold the head at an angle so that the gasoline goes towards the valve seat through the port. If the gasoline doesn't immediately begin to seep between the valve head and seat (should take a few seconds until it does), you're good. If it seeps / pours right through, a valve job is in order.
But don't stress yourself too much. Remember that these are simple machines built to run even if they hurt a lot. Before properly repairing the heads on my bike, they had worn valve guides, two of them had been press-fitted in the heads from the wrong direction, the valves were leaking and so on. Still started on the first kick, idled and ran.
Valves - setting the clearance
Easiest way to set the valves is to bring the engine to TDC (there is usually a "///" or "B" mark for TDC on the flywheel just after the "P" mark, as explained below) two times. First for a piston, then for the other. If there's no mark for TDC on the flywheel, just take out the spark plugs and use a screwdriver or any other sort of relatively rigid feeler through the spark plug hole to tell when the piston is at its furthest out. At that point, one of the pistons will be between compression and combustion, meaning that its corresponding valves should be completely shut and there should be a gap between the rockers and valve stems. Check the gaps on that side now.
The manual wants a fancy, pretentious, BMW-airhead-like 0,07 mm gap between rocker and valve (with or without that valve cap, forget about it if you don't have it). I found that a loosey 0,1 mm gap allows for all manner of Dnepr-like expansions and will harm naught. If the rocker has a lot of axial play on its shaft between the aluminium mounting pegs, this is a great time to shim that play out. Leave just a wee bit for expansion. Double-check your work and then rotate the crankshaft another 360 degrees to bring the other piston between compression and combustion. Check it, set it.
Ignition - timing
In Dneprs, I noticed that the left cylinder also tends to act funny (particularly at idle) when the timing is too advanced (spark occurs too early). Might also have to do with the lobe placement on the camshaft, apparently there aren't two identical ones out there.
Anyway, one way to set the timing is to pull out the rubber plug out of the crankcase on the left side to reveal the flywheel inspection hole. Gently hand-crank the kickstarter until a P mark appears on the flywheel (keep eyeballing it through the inspection hole). Take off the unbelievably thick aluminium timing cover off the engine (the one behind the front wheel, it's fastened by a single 14 mm nut to its stud) and, after that, the small tin cover off the timing advance mechanism. Now turn the ignition on and (I assume that you've got the mixing-bowl-of-doom-type centifugal advance ignition on your MT-11, see second picture below) use a relatively small flathead screwdriver to pry the timing cam's counterweights apart. The spark should occur when the counterweights are completely open. If not, adjust the stator by means of loosening its bolts and rotating it either way. If you've got the newer Russian / Ukrainian electronic contactless ignition, forget about checking the counterweights - there are none. Just get it started (advance it if you have trouble firing it up) and then jiggle it around. Or viceversa. :)
Regardless of the ignition system, I strongly recommend you proceed to manhandle this setup after you get the engine running. It'll often be the case that a better timing advance will be achieved on-the-fly. Slowly retard or advance it while it's running until you get the highest stable idle rpms. Keep in mind that carb tuning does influence this. Too much advance will cause detonation - you'll know you've advanced it too much when the idle goes rough and the bike starts potato-potato-ing like a Harley. Retard it too much and you'll get a rock-solid idle, but you'll also make it the slowest thing on the planet.
Ignition - coil
As others have pointed out, I wouldn't rule out coil woes. The original hand-wrapped coils are nigh crap, and so are their seemingly more evolved successors that have traded textile wrapping for shrink-tubing. Went through a handful of either of them until I gave them up. Would they spark? Yes. But would they work properly? Nope. Difficult starting, colossal stuttering at low revs, intermittent cut-offs on acceleration (opening up the throttle would let in lots of gas that the weak spark would be unable to ignite).
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Having just replaced a sexy Nippon-Denso twin coil yesterday due to it shorting out from overheating, I can say that you should not believe a spark when you see it. Bike went dead all of the sudden - always happens in a convenient place, this time right in front of my home after three hours of unbelievably thick traffic on a warm spring day. Checked everything, leaving the coil for last - would you suspect a coil right off the bat if it was sparking? I didn't, thought it was the contactless ignition to blame. Hell, it even fired on one cylinder after I changed the plug with the rustiest spare I could find (always the best plugs!), though the idle was clearly rough and would die off after a few seconds of sputtering. The spark was visibly weak, a thin white asthmatic spark. Blame it on the sunny weather at first. An ohm-meter then revealed that the bad coil had a resistivity of 2,4Ω instead of the 3,7Ω shown by a good one. To my simple mind, this means there's a short in it somewhere and that it can no longer produce that high a voltage to generate a strong spark.
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A year ago, when I installed this coil as a fix-all solution to my ignition woes, I didn't give its placement a good thought. At the time I was just too happy about having found a Japanese coil that fit in place of the original without modifications. It did indeed run great while it lasted. But these engines run HOT and them engineers picked a bad place to mount all this sensitive electrical equipment. It was probably less of an issue when they came up with the idea sixty years ago, with all that three-cars-a-day-traffic and cooler Ukrainian climate. Not to mention the occasional water-cooled (read: snow- / river- / bog-cooled) adventures.
So if you can pick up a higher-quality twin coil like this one (off a '90s Suzuki GSXF and quite a few other models, I think), do so. Just try your best to install it someplace cool, maybe externally, if space is abundant and clean looks are not your main concern. Or put some serious holes in that aluminium cover to help cool stuff down.
Over here, due to a soon-to-be-history abundance of old cars and motorcycles, we sometimes have an easy time locating 6-volt coils. You can use an alternate coil setup (BMW airhead style) with two 6-volt single-lead coils. One HT lead for each cylinder. Connect the coils in series: to do that, identify the positive and negative connectors on both of them, they've got one of each; run a kill-switched +12V to the positive terminal of one of them, then run a wire to connect that coil's negative to the other's positive; the negative of the 2nd coil connects to the ignition contact breaker (classic points or whatever replaces them now). They're going to work as a single 12-volt coil, but each will have its HT lead connected to a separate spark plug. Got a friend whose '69 M63 Ural works like a charm using this setup.
You said you already tried swapping carburetors to no avail, so they're probably not the main culprit here. When they do step forward as the next thing that has to be set, pick one side and screw in the carb's mixture screw (they be vertical, on the side, just above the float chamber) until the rpms drop, then slooowly unscrew it until you get the highest stable rpm on that cylinder. After that, reduce the idling speed (if it's considerably higher now) by screwing in the top bolt (K-63 / K-65) or unscrewing the small side screw (K-68 / Karteh VDC-03). Repeat until you needn't adjust it anymore, then move on to the other side. Keep your cylinders ventilated if you're going to do it for long, a simple fan or two will do the trick. And take off that timing cover while you do it!
Water in the float chambers is a reality for these carbs and they don't really like it in huge amounts. Good luck! Let us know what you find. ;)
Posted 12 April 2015 - 08:52 AM
Good for you Muravey
Posted 12 April 2015 - 03:51 PM
Posted 12 April 2015 - 05:42 PM
As @Shoetou pointed out, these float needles rely on an o-ring to shut off gas. Kind of makes you wonder why they bothered to make them resemble actual working float needles in the first place. As a quick roadside fix, we would buy a cheapo refillable gas lighter, break it apart and salvage the valve o-ring. It fits on the carb float needle, but some of them are made of low-grade rubber and expand somewhat after prolonged exposure to gasoline. Get rid of them if they do and buy another lighter. :)
Can't wait to see some pictures and vids of your bike.
Posted 13 April 2015 - 08:18 AM
If the think has those o-ring float needles...It is Crying for Walboro needles...Made an Unbelievable difference in my MT-11
BTW When switching to Walbore Needles, make sure that one of the o-rings does Not get left behind in the Seat!
Ask me why I know that!
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