Yamaha TW200 Trailway Discussion Forum

Search Sort Posts:  Oldest to newest Newest to oldest

03-02-2010, 8:30 AM MacBookProTW Joined on 08-04-2008 Salem, Oregon Posts 94 Re: Sounds rough at lower RPMs okay so I have been a bit busy at work so here is an update. I changed the title to match more closely what is actually happening here. I have not tested the electrical yet, but here is what is going on. If I let out the clutch and let the engine get a bit of a load and then hit the gas there is no stalling. If I let of the throttle at speed and slowly apply throttle it sputters until there is a load on the engine. I'm at a loss now as to what this could be. I really don't want to go through and start replacing a bunch of expensive parts and in the engines defense it runs like a freaking top under load. It accelerates great with good get-up-and-go. What are some good tests I could do and where to start? Could this be the boot around the carb causing a vacuum leak or that stupid tube for the california stuff that leads to nowhere off the top of the carb boot? some people's kids    Report

03-02-2010, 8:57 AM TW-87 Joined on 02-01-2010 Manitoba, Canada Posts 305 Re: Sounds rough at lower RPMs If it only sputters when the engine is slowing down ( you are rolling back the throttle ), it could be the enricher circuit. That's the diaphram on the side of the carb. You previously said that the bike starts and idles well when cold, and runs well under load. That means your ignition is probably okay. Your pilot circuit (pilot jet and screw) is not lean or it would not idle well when cold. Your pilot circuit is not rich or it would run better when you turned the pilot screw in (fewer turns out). So your pilot circuit mixture is probably okay. Any air leaks on the engine side of the carb would screw up your idle. TW-87 1987 TW200, 15/44 sprockets, DID O-ring chain, Award winning, "Quick Release" Action Packer :-))    Report

03-02-2010, 9:04 AM MacBookProTW Joined on 08-04-2008 Salem, Oregon Posts 94 Re: Sounds rough at lower RPMs It is when I roll off the throttle some, but mostly when I go to roll on the throttle before it catches up and puts a load on the engine. How do I fix that enricher circuit or test for that? some people's kids    Report

03-02-2010, 10:32 AM TW-87 Joined on 02-01-2010 Manitoba, Canada Posts 305 Re: Sounds rough at lower RPMs You have to pull the carb and disassemble/clean/inspect that part of the carb. You may be able to find something on this forum using the search feature. Before you take the carb apart, you can disconnect the short black hose that runs along the side of the carb and (with your mouth) suck air out of the diaphram area then cover the hose with your tongue - no it's not sanitary, but how bad do you want to fix it ? If the diaphram will hold a partial vacuum for a few seconds then you know it's intact. If it's good, you'll feel a "pop" on the end of your tongue when you pull it off. Once you disassemble this mechanism you'll see how it works. check an on-line parts schematic to confirm that all the parts are there and in the right place. Note that carb cleaner can ruin rubber components like the diaphram or o-rings. TW-87 1987 TW200, 15/44 sprockets, DID O-ring chain, Award winning, "Quick Release" Action Packer :-))    Report

03-02-2010, 10:41 AM MacBookProTW Joined on 08-04-2008 Salem, Oregon Posts 94 Re: Sounds rough at lower RPMs oh I know how to take it apart as I have done a few times. Now that you mention it it looked pretty beat up before and has that weird brass end to it. I will check it later today when I get home. If that is it I totally owe you a beer man or a case. I could care less if it is sanitary if it fixes the problem. My guess is that I cleaned it and the cleaner got up in there if I hadn't taken that part off or something, but we shall see. P.S. I like your picture, but it scares the crap out of me some people's kids    Report

03-02-2010, 10:50 AM TW-87 Joined on 02-01-2010 Manitoba, Canada Posts 305 Re: Sounds rough at lower RPMs Good luck, and sorry about the scare.  It's just a halloween mask. I chose it because it looks like I feel when I get up in the morning ! :-)) TW-87 1987 TW200, 15/44 sprockets, DID O-ring chain, Award winning, "Quick Release" Action Packer :-))    Report

03-02-2010, 7:30 PM Woofhound Joined on 03-02-2010 Cle Elum/Federal Way, Wa Posts 110 Re: Sounds rough at lower RPMs Hi, new member here but fairly knowlegable on bikes. you didn't mention whether you checked valve clearance or not. it sounds to me like you might have a tight valve or a clogged idle fuel passage. if the valves are fine, then blow out the carb with carb cleaner and an air nozzle. you might also try spraying a little carb cleaner on the intake manifold while it is idling and see if you get any changes in idle which would indicate a leak. good luck    Report

03-02-2010, 7:51 PM MacBookProTW Joined on 08-04-2008 Salem, Oregon Posts 94 Re: Sounds rough at lower RPMs My first post I said I checked valves first. I also have cleaned the carb at least 3 times now with cleaner and compressed air. What would carb cleaner on the intake do? And what would I be watching for? Exactly where do you mean to spray it? In the intake side of the carb or around the intake boot to check for leaks? I'm open to testing just about anything, but I have to know why. some people's kids    Report

03-02-2010, 8:06 PM MacBookProTW Joined on 08-04-2008 Salem, Oregon Posts 94 Re: Sounds rough at lower RPMs Well if I am trying this correctly you may be on to something clown man. I didn't remove the carb as I cleaned it this last weekend again for the third time. I carefully sucked on the hose and got some pressure but it did not hold my tongue with suction at all really. It would slightly for a second but there was no popping going on. Did I do this righ or does it need to be apart and I block something else off to do this test? some people's kids    Report

03-02-2010, 8:31 PM TW-87 Joined on 02-01-2010 Manitoba, Canada Posts 305 Re: Sounds rough at lower RPMs Mac. It sounds like you did it right. Rolling back the throttle causes the intake pressure to go way down below atmospheric (I.E. high vacuum condition). This vacuum is supposed to pull the diaphragm out and a little brass piston that's connected to it to open the enricher circuit. The enricher circuit supplies enough fuel to the engine to keep it firing even under this "starvation" condition. Without this, the engine would mis-fire for a few revs at a time allowing fuel to build up in the exhaust system. After a few revs without firing, the cylinder accumulates enough fuel to fire and guess what happens in the exhaust system.... Sound familiar ? These are the parts as shown on the mrcycles.com exploded diagram:         # 32       DIAPHRAGM SET     1        5Y1-1490A-00-00 When I tested my diaphragm this way, it held the vacuum for at least 10 seconds. Clown Man TW-87 1987 TW200, 15/44 sprockets, DID O-ring chain, Award winning, "Quick Release" Action Packer :-))    Report

03-02-2010, 8:44 PM MacBookProTW Joined on 08-04-2008 Salem, Oregon Posts 94 Re: Sounds rough at lower RPMs Yes it is worse just starting out and seems like it won't even build up until I put full load on the engine. It doesn't pop or seem to do anything while letting off the throttle though. And I can hold a steady low RPM as well and make it sputter some. Could that all be caused just by this flipping rubber thing? some people's kids    Report

03-03-2010, 8:04 PM TW-87 Joined on 02-01-2010 Manitoba, Canada Posts 305 Re: Sounds rough at lower RPMs I can't say. Please allow me to be blunt. ( there is a question of free beer hanging in the balance) I can say that if your enricher diaphragm won't hold a vacuum using the test I described, then your carb is broken. It may also be out of adjustment. However, you can't adjust it properly until you fix the broken parts first :-)) TW-87 1987 TW200, 15/44 sprockets, DID O-ring chain, Award winning, "Quick Release" Action Packer :-))    Report

03-18-2010, 9:27 AM MacBookProTW Joined on 08-04-2008 Salem, Oregon Posts 94 Re: Sounds rough at lower RPMs Okay, so 90% of the problem is totally gone now. It does have a slight hesitation when dropping the throttle and throwing it back on around 40mph in 5th gear, but I think that is the nature of having a carb and I'm pretty sure it did that before. I think now that it is running a bit rich due to having backed the pilot screw out to 3 turns. It was originally around 1/2 turn out. Thoughts? some people's kids    Report

03-18-2010, 2:34 PM TW-87 Joined on 02-01-2010 Manitoba, Canada Posts 305 Re: Sounds rough at lower RPMs Was it the enricher diaphragm ? If so, you owe me a beer ? TW-87 1987 TW200, 15/44 sprockets, DID O-ring chain, Award winning, "Quick Release" Action Packer :-))    Report

03-18-2010, 2:39 PM MacBookProTW Joined on 08-04-2008 Salem, Oregon Posts 94 Re: Sounds rough at lower RPMs Yes that is what got me to 90% better. Now I'm messing with the pilot screw some. It still sputters a tiny bit after moving the pilot screw back to 1 turn out. I do owe you a beer. If you were near Salem Oregon I would pay up tonight. some people's kids    Report

03-18-2010, 3:02 PM TW-87 Joined on 02-01-2010 Manitoba, Canada Posts 305 Re: Sounds rough at lower RPMs Sorry, I can't make it tonight. But I'll keep that beer in mind next time I'm in Salem............ Clown Man TW-87 1987 TW200, 15/44 sprockets, DID O-ring chain, Award winning, "Quick Release" Action Packer :-))    Report

Page 2 of 2 (41 items) < 1 2

Yamaha TW200 Tr... » TW200 Forums » TW200 Technical... » Stalls except under load - Changed Title to clarify problem

(please select) Forums Home |- Search Forums |- Active Topics |- Unanswered Posts User Options |- Sign In |- Join this community |- Forgot Password TW200 Forums |- TW200 General Discussion |- TW200 Technical help |- Trails, Offroad, and Adventure Riding |- TW200 Classifieds |- TW200 Performance and Customization Other Forums |- Off-topic and other bikes |- Forum Feedback