harryharls Posted April 11, 2017 Report Share Posted April 11, 2017 Hi, My Evo just seems to be a bit sluggish at times in terms of throttle response. On some occasions when I want to blip the throttle to hop up over a log or double blip over an obstacle it just doesn't respond quite as I'd like it to. I'm going to strip the carb down to give it a clean and while I'm there I'll check the reed valves. Has anyone got any suggestions for what it might be other than this? I can't seem to find any info for stock/standard carb settings for it, I'll check the jet types whilst I clean the carb but without stock info I don't' know if they're the right jets or not! If anyone could let me know what standard jetting settings should be that would be brill! Cheers, Marcus Quote Link to comment Share on other sites More sharing options...
dan williams Posted April 11, 2017 Report Share Posted April 11, 2017 My experiance with the Keihin carbs is the pilot circuit gets blocked because the exit oriface behind the slide is TINY. Even a droplet of water is enough to seal it off. When that happens the whole carb should be taken off, disassembled and blown out with compressed air. If you take the jet tower off (requires security torx bit) be VERY careful not to damage or lose the rubber ring gasket at the base of the tower. What you describe could very well be a blocked pilot circuit. Typically the bike starts running sluggish off idle so you turn the idle speed up which keeps the engine running but makes for some inconsistant behavior at low rpm. Quote Link to comment Share on other sites More sharing options...
lineaway Posted April 12, 2017 Report Share Posted April 12, 2017 Dan might have the answer. There is a term some use and I can`t remember it. It`s like the death burble or something like that. The worst thing is Keihin does not sell the rubber parts to the tower. 2nd thing is soaking it in carb cleaner could make it even worse.. Quote Link to comment Share on other sites More sharing options...
harryharls Posted April 12, 2017 Author Report Share Posted April 12, 2017 Thanks for the replies, I'll disassemble the carb and give it a clean out...thanks for the tip about the rubber seal, does the jet tower have to be removed? Does it have to be removed to access the jet? In terms of the way it runs, it starts, runs and idles perfectly without any issues at all. It's just that I feel it's a bit slow to respond sometimes, it can catch me out when navigating an obstacle and I need a quick response. I know these UK models have the flywheel weights fitted, could this slow the response at low revs? Thinking about it, another thing I notice about this engine is that it's very slow to return to idle after being revved high (in neutral), I presume this is the flywheel weight but could it (and the slow response) be a symptom of a leaky reed valve? Quote Link to comment Share on other sites More sharing options...
harryharls Posted April 12, 2017 Author Report Share Posted April 12, 2017 Just looking at some Boyeson carbon reeds on a website, the description of their benefits looks kind of related to the issue: Boyesen Reeds Carbon Tech for Beta Evo 250, 290, 300 THE BENEFITS:- Quicker throttle response and acceleration.- Easier to Ride, crisper Low RPM riding.- Crisper, smoother transition from Low to Mid.- Connects your hand to the power.- Longer life - Boyesen Power Reeds outlast all other aftermarket reeds. 1 Quote Link to comment Share on other sites More sharing options...
guy53 Posted April 12, 2017 Report Share Posted April 12, 2017 The fact that it is slow to return to idle point you in another direction, air leak ? Guy Quote Link to comment Share on other sites More sharing options...
totty79 Posted April 12, 2017 Report Share Posted April 12, 2017 What you're describing is very subjective and could just be the flywheel weight (however it would be 100% consistent), or it could be the range of other issues that have been suggested. If it is consistent then I'd try to compare it to another 250 evo before changing anything. Quote Link to comment Share on other sites More sharing options...
dan williams Posted April 12, 2017 Report Share Posted April 12, 2017 Carbon reeds do help the low end torque. I put VForce reeds on any new bike I get but the carb clean is the place to start. If that doesn't fix it you can look for an air leak. Typically done by spraying small amounts of hot start fluid around the cases of an idling engine and listening for a change of speed. This is of course dangerous as hell so must be done in tiny shots with an extinguisher at hand. You do have access to the jets without removing the tower and you can blow air through enough holes to clear out the pilot circuit with the tower still on. Quote Link to comment Share on other sites More sharing options...
harryharls Posted April 12, 2017 Author Report Share Posted April 12, 2017 Great stuff, thanks Dan. It's in bits now actually and it was pretty dirty (relatively speaking) in there to be honest.Unfortunately I don't have a compressor/airline but hopefully a few squirts of carb cleaner or similar will suffice. I've already cleaned it through with fresh petrol. The jets and needle/clip position are all standard luckily so hopefully a good clean will restore it to full working order. I'm going to take the reed block off now and inspect that, I still suspect that may be the problem but we'll soon see. If this doesn't work I'll check for an air leak. Quote Link to comment Share on other sites More sharing options...
harryharls Posted April 12, 2017 Author Report Share Posted April 12, 2017 After taking the reed block out I can see that the reeds are in perfect condition with no fraying or gaps, however there was some water in and around it! I can also see a bit of emulsification of the oil on the surface of the crank as I turn the engine. The water seems to have got in by the gasket between the reed block and the case, presumably from cleaning it. I guess if water can get in there then air certainly can so it looks like you both may be right about the air leak. I'll put some hylomar on the gasket and see how it goes. Quote Link to comment Share on other sites More sharing options...
dan williams Posted April 12, 2017 Report Share Posted April 12, 2017 I like how Beta paints the reeds black to look like carbon fiber but under a microscope the fibers are clear so fiberglass. Small amounts of water can get into an engine all kinds of different ways so it's not a great indicator of leaks. Certainly not intake tract. 1 Quote Link to comment Share on other sites More sharing options...
dan williams Posted April 12, 2017 Report Share Posted April 12, 2017 Oh and in a pinch one of those cans of compressed air from a camera shop can be used to blow out a carb. Quote Link to comment Share on other sites More sharing options...
harryharls Posted April 22, 2017 Author Report Share Posted April 22, 2017 Just to update on this; it's running beautifully now after the carb strip and clean and proper sealing of the reed block gasket. I'm running the air screw at 2 full turns out (manual states 2 1/2 turns out) with all standard jetting and standard needle clip position and it's perfect. I still am tempted to fit some Boyeson or similar carbon reeds in there though to hopefully give it a bit more snap :-) Quote Link to comment Share on other sites More sharing options...
dan williams Posted April 25, 2017 Report Share Posted April 25, 2017 That idle mixture screw is a pain in the A** isn't it. I have a whole bunch of long flat blade screw drivers ground to size and scattered all over my car and garage just so I have one handy at all times. I tried one of the Jitsie mixture screws but it was worse than the stock one. The older bikes had a screw soldered to a cable but I guess Beta gave up on that idea. The carbon reeds won't seem snappier but they will let you pull a gear higher without stalling. It actually will come off idle a bit cleaner because the carbon reeds open and close faster because they weigh less so they will enhance the fuel air charge in the crankcase at low rpm. At high rpm the reeds could be made of lead and it wouldn't make any difference because they just stay open anyway. I always love to read someone bragging about how carbon reeds make their bike faster. Goes along with the, "My bike is faster because it has the RED powerband" Quote Link to comment Share on other sites More sharing options...
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