BW200...ssssssllllllllllloooooooowwwwww

[Six Stroke]

I had no presumption that the BW was going to be a ball of fire, what with all those chains and sprockets. However, I've noticed that I'm always riding it WFO, whereas my DX and 200E don't need nearly as much throttle. It just doesn't rev. It'll get to a certain (unknown, because, well, no tach) rpm and just hang there. No popping or sputtering, just a flatline. Looking around on the interwebs has cast some light on a possible cdi problem, but are these typical symptoms? After a couple miles it doesn't like to idle very well, and pops on decel most of the time. Any insight from the BW gurus?

[hoosierlogger]

Mine is slow too. They are not speed demons, but will go almost any where.

[Vealmonkey]

They are not really meant to run constantly wide open, so that is more than likely the reason it acts the way it does. You are killing your own machine dude. There are little things that you can do. Change sprocket gearing, run a free flowing type exhaust and run a more free flowing air filter which will give you a little more speed. Heck, you can even run a different cam, but they just weren't meant to be speed demons. More for pleasure riding and pretty much riding through anything.

[Six Stroke]

They are not really meant to run constantly wide open, so that is more than likely the reason it acts the way it does. You are killing your own machine dude. There are little things that you can do. Change sprocket gearing, run a free flowing type exhaust and run a more free flowing air filter which will give you a little more speed. Heck, you can even run a different cam, but they just weren't meant to be speed demons. More for pleasure riding and pretty much riding through anything.

Perhaps I should be a little more clear. It flattens out at a pretty low RPM and it has no balls up to that point. The DX and YTM200 are the same engine platform and are also geared pretty low, but don't feel nearly as anemic. Popping the front up over an obstacle? Nope, not happening. I've played with the jetting a bit and it runs better without bogging now, but it seems as though the timing just doesn't advance.

[DohcBikes]

So you played with the jetting and it got better. What did you change? Kinda sounds lean or like carb might be dirty.

[Six Stroke]

Raising the needle to the richest setting took care of a nasty stutter when you tried to get on it, but overall the low-RPM cap hasn't changed. Stock main is a 108, currently it has a 112, and I had a 115 in when it was super cold this winter. Changing main jets hasn't really done much, as there's virtually no difference between 1/2 throttle and full throttle. I would almost think the slide wasn't opening fully, but it is. For the record, it has a new Wiseco 10.25 piston and freshly lapped valves, and the valve lash has been checked several times. Exhaust is stock, though the muffler is missing the spark arrestor insert and the baffle isn't baffling as much as it should. Carb is stock (other than the jetting), and the air filter is a new OEM piece. Gearing is stock, and the rear tire is a 22" skin.

[DohcBikes]

Did you do a compression test? Leak down test? These are critical for diagnosing a fresh engine that has issues.

Ride it, put the 115 back in, see if it got ANY better, even a tiny bit better means you are lean. Considering raising the needle to the richest position helped the off idle issues, your pilot is definitely at least one size too small, but that doesn't address your 1/2-WFO throttle problem.

Did you measure your cam when you rebuilt it? It could be worn. Don't rule this out in the event that you can't figure it out.

Are you 100% positive of correct cam and ignition timing?

Have you tried another CDI?

Have you tested your trigger coil resistance?

These are a few of the many things that can cause power loss.

[640AK]

Six Stroke,

Your problem doesn't sound like a CDI issue. In my experience, the bike will lose the ability to run in the upper RPMs completely but will still idle normally. If you short shift the bike and keep it at idle, you can usually make it back home but any load on the engine will cause the engine to quit running.

Since your jetting changes have had some effect, your carb could be the issue. The cheap Chinese carbs on ebay have been getting pretty good reviews and would remove jetting from the equation. They are pretty cheap since they are counterfeits.

Some of my 350 carbs are so worn that they can't be tuned anymore. At least there are replacements available for the 200s.

[jb2wheels]

I had a kick start on BW200. It was geared like a tractor and would climb straight up a wall.

It was slow, but it would rev. Engine ran like a 200X engine.

[Six Stroke]

Did you do a compression test? Leak down test? These are critical for diagnosing a fresh engine that has issues.

Ride it, put the 115 back in, see if it got ANY better, even a tiny bit better means you are lean. Considering raising the needle to the richest position helped the off idle issues, your pilot is definitely at least one size too small, but that doesn't address your 1/2-WFO throttle problem.

Did you measure your cam when you rebuilt it? It could be worn. Don't rule this out in the event that you can't figure it out.

Are you 100% positive of correct cam and ignition timing?

Have you tried another CDI?

Have you tested your trigger coil resistance?

These are a few of the many things that can cause power loss.

Funny thing is that it almost seems too fat on the pilot. No matter, since pilot jets for those TK carbs are quite elusive. 640AK's suggestion was the next step on my list: going with one of the cheap replacement carbs. They're inexpensive enough to be an easy option. Cam timing is on, but I have yet to check the ignition timing, which is also one of my "next steps." Trouble is I don't have an inductive tach, so I'll be dragging the BW to somebody else for that. The CDI problems on these bikes sound pretty frequent, but the general consensus here is that it isn't the problem, which makes me pretty happy.

[DohcBikes]

A general consensus doesn't diagnose or fix a bike. It needs tests to eliminate possible causes, and making assumptions over the computer is a great way to skirt around an issue. The general consensus in the beginning was that your bike is just slow, which is also an assumption.

What I am suggesting are actual tests for common issues that I have in the past personally and frequently diagnosed as the cause for symptoms you are describing. Thats really all we can do from here.

[Six Stroke]

A general consensus doesn't diagnose or fix a bike. It needs tests to eliminate possible causes, and making assumptions over the computer is a great way to skirt around an issue. The general consensus in the beginning was that your bike is just slow, which is also an assumption.

What I am suggesting are actual tests for common issues that I have in the past personally and frequently diagnosed as the cause for symptoms you are describing. Thats really all we can do from here.

Considering that the next opportunity to work on the bike is Sunday (if I have time even then), supposition and consensus is all I have to go on at the moment. I never meant to give the impression that I wanted a magical internet fix out of laziness, rather my purpose is to gather ideas for when I can actually work on it. My initial plan was to check the timing and replace the carb, but various internet searches revealed that BWs are known to have CDI problems. Just trying to cover all my bases here and find out if the symptoms are similar to that of a faulty CDI, since I would rather not drop $300 on a new one just on a hunch.

[DohcBikes]

The best way to check a CDI is to swap with a CDI from a bike that runs the way you want yours to. Resistance checks ar possible but not reliable.

I dont necessarily think its the CDI, its just a possibility. Why are they 300 dollars?

Why are jets hard to find? have you tried jetsrus, have you tried your yamaha dealer?

[Six Stroke]

The stock TK carb is a weird little Mikuni knock-off, and while the main jet can swap with the round, slot-head Mikuni mains, the pilot is something different. And strange. The stock pilot is no longer available (from Yamaha), so I'm not holding out hope for any non-stock sizes. I guess it's a common brand of carb for scooters, and those scooter folks have the same pilot-rarity issue.

A new CDI is about $290 from Bike Bandit, about $100 cheaper than list price. It's a 7-wire box that was used only on the '85-'86 BW200, so again, rare parts. I do have a pair of 6-wire boxes from a Yamaha dirt bike, and my DX/200E have 8-wire boxes. I'm going to intently study the wiring diagram to see if either one of those options can be made to work just for a test. I'm also waiting to hear if the local small-engine guy has an inductive tach and timing light so that possibility can be eliminated.

See, the thing is, I'm fine if it's slow but running correctly. It's this problem of no revs/no throttle response/backfiring on decel/refusing to idle when hot that's got my goat.

[hoosierlogger]

Is your BW 200 electric start or kick only? I have an extra CDI for kick only. It is known to be good.