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Post by bikerdude on Mar 4, 2012 10:24:11 GMT -5
I have a cf 250 in a viper trike. Ran well, so i started upgrades. replaced the 28mm auto choke carb with a oko 30mm manual choke and uni filter. Starts instantly run well up to wot then starts cutting out. How can I determine if its carb, ignition or the rev limiter doing its thing. re jetted way up and way down same thing. Just changes the color of the spark plug from white to chocolate, left it at a nice tan..Just put a temp atv gas tank on with 1/4 inch hoses new petcock 1/4 inch fuel filter into carb direct. Same thing! No tack. Even in neutral cuts out at wot?  ? Any ideas? |
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Post by bikerdude on Mar 4, 2012 15:02:12 GMT -5
It stumbles a bit clears and revs normally, I increased the main jet 5 sizes larger one step at a time, no diff just made plug black, went 5 sizes smaller one at a time, same thing no effect just made my plug white! still stumbles.. Its right at about 55 on the highly accurate china meter lol. Never did it before with old carb, as it never got that high in rpm. If I back off it just ocasionally pops or cuts out 1x in like 5 min Idle is solid, starts perfectly, no decel pops either... Im stumped? |
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Post by bikerdude on Mar 5, 2012 0:35:45 GMT -5
Removed the vacuum carb 28mm and replaced with oko 30mm with flat slide, removed all hoses has manual choke. Had a lot of problems with stock carb, erratic idle, electric choke sticking. one day would be perfect next sluggish. replaced intake carb and air filter. Jet has been replaced till plug was black. so stepped it back down one step at a time for a tan plug. None slightly changes darn cutting out happens every time. 3/4 no problem  |
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Post by skuttadawg on Mar 5, 2012 1:21:55 GMT -5
Turn the fuel/air mixture screw an 1/8 or 1/4 turn and see how that does after its running and the engine is warm prior to adjusting it . Most stock have a cover over the screw and aftermarket are accessible . Do you have stock exhaust ? With a uni you get more air in a need an unrestricted exhaust to get the excess out faster than when restricted . Stock has a cat while HP does not thus much better flow . Do you have a rev limited cdi ? Even some unlimited do not have a timing curve and cut out at high rpms so replace with unlimited with timing curve may help and around 30+ Popping can be a lean misfire or vacuum leak . Backfiring means timing is off and ignition happens when the exhaust valve is open instead of closed like it should be to retain compression in the ignition cycle . With all of the carb issues think about going with EFI . My Echarm has a Ducatti EFI and it starts instantly at any temp , gets better mpg , has electric fuel pump instead of diaphragm mechanical and I can out run any 150 with ease as its like a rocket with way more power than carbbed 150s I have ridden and raced . I an undeafeted as of today woohoo ! EFI kits here www.mbe-motorsports.com/catalog/index.php/cPath/22?osCsid=mrdg4avagrlnvn45ietov2omi7 . Most stock fuel pumps can not deliver enough fuel at high rpms so maybe you can try this pump made by Mikuni ( the best ) and cheap as well as simple to install . Also maybe try a new fuel filter since only 3 dollars and your may be clogged but not so that it prevents flow just limits if clogged . Do a compression test with a gauge and throttle wide open to allow in the max of air to get a correct reading . If below 125 psi maybe some rings will help . Have you checked your valves as all 4Ts the valves need adjusting as part of maintenance . If you are going for top end then maybe a HP cam will help you get more fuel and air into the engine . Hope this helps if not please do not use a hammer to fix it lol |
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Post by skuttadawg on Mar 5, 2012 1:55:00 GMT -5
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Post by bikerdude on Mar 6, 2012 21:55:05 GMT -5
Just put a non limit cdi coil combo, same thing cuts out bad at full throttle. Will try valves, Plug looks good. Loosened muffler to get less back pressure, same thing.. Going crazy.
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Post by skuttadawg on Mar 6, 2012 22:04:34 GMT -5
unis are harder to tune andallow water to get in your engine try replacing the air box then see how it runs and do a plug chop to check the jetting
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Post by bikerdude on Mar 6, 2012 22:05:48 GMT -5
Is the needle still at play a wide open or is it just the main jet at that point.. May need to investigate that any input???
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Post by bikerdude on Mar 6, 2012 22:08:07 GMT -5
You mean put the stock air box back on? Ok Great Idea. will try that also
Thanks for all your input!
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Post by skuttadawg on Mar 7, 2012 1:42:06 GMT -5
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Post by bikerdude on Mar 7, 2012 22:24:41 GMT -5
Yep, got that, explains the white plug when I do the WOT engine kill. Was not doing it properly, rode it hard, then back home, idled a bit then was checking plug. New CDI from kidnme with integrated coil helped, but still way too lean. Will keep you guys updated. Stock box on the viper trike has alot of extra places for leaks poorly made. Could get no idle and 35 with that.. and it rattled bad mounted with 1 screw, sooner not have that. Could modify it. will try.. Valves were still adjusted perfectly. THX
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Post by skuttadawg on Mar 8, 2012 1:33:27 GMT -5
With EFI you never have any hassles or run too lean , more performance and MPG . Its around 400 and might not be just a simple bolt on and some tinkering required but once its done you will be glad you did and enjoy your trike even more .
Lots of people think the airbox chokes the air but it does not and it keeps out dirt and water better than a Uni or K&N . Yes having an airfilter mounted on the carb will have much better flow than through a tube but will require upjetting and several plug chops to get it right .
Replace the Teflon intake with an aluminum one to avoid any vacuum leaks like when the Teflon gets holes or cracks as the dry up , more so if exposed to sunlight like a motorcyle which is open and not covered like a scooter is . A rag with a tiny amount of tire dressing sprayed on it , you can wipe the intake to replenish any lost oils in it so it lasts longer .
Tuning is a learning curve and fun too . I am willing bet ALL of us had made mistakes and learned from them , thats why it so important to do your homework first so you do good on the test . I said that to help you visualize better the point I am trying to get across rather than blah blah blah etc .
Wrenching is fun when you do not have to and a great skill to know when you have a time that you have to wrench
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Post by bikerdude on Mar 10, 2012 18:04:59 GMT -5
Put stock 28mm carb on today, no hesitation runs full throttle. Carb has security screws on bowl cant see what its jetted at. Goes about 50 mph with full throttle.
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Post by bikerdude on Apr 18, 2012 6:05:47 GMT -5
Got a nice aluminum carb intake from knm parts, bit pricey but now can correct stupid rubber boot intake. this one also is not on an angle. Wont need a bracket to hold the back of the carb up, hopefully!
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? Any ideas?