TT250 hiccup - Page 3

moparrob · 12-13-2016, 02:34 PM

Quote:

Originally Posted by Weldangrind

I was recently trying to drill out a slow jet with a 61-80 numbered drill set (and a pin vise), when it all went pear shaped on me. I couldn't make any sense out of what was happening with the motor, since it was behaving like it was getting way more fuel than I was providing. It hit me a few days later; the drill bits were incorrect from the factory. I had drilled the jet out way too far.

I took each bit out and measured with a vernier, and discovered that of the 19 bits in the index, I only had six sizes (which were triplicated). I've learned to measure the bit before I happily drill away, so I don't unwittingly go too far.

I didn't think I'd have any success in filling a slow jet with solder. Since I had another virginal jet, I drilled it to the correct size (according to Mr.Vernier) and the motor was happy.

I used a micrometer as well since I did not trust the size of the drills as indicated.

moparrob · 12-24-2016, 05:43 PM

I had a chance to do some more research on the issue and now believe the jetting changes I made are appropriate (117 Main).

I have 2 identical bikes, a white one and a black one. The black one was the one that had the problem. I have since rejected the white one to be identical to the black one and it runs perfectly, without any hiccups. I have taken it on some sustained (indicated) 65 mph runs with no problems.This leads me to believe that the jetting is not the problem with the black bike which still hiccups.

So the next likely problem would be the installed air injector emission control.I know there is a permanent way to block it off with a plate but does anyone know if you can temporarily disabled it by simply disconnecting and plugging the vacuum port and hose? I would like to isolate that as being a problem before I take any further measures. Thanks again for the input.

pete · 12-24-2016, 05:57 PM

Quote:

Originally Posted by Weldangrind

I was recently trying to drill out a slow jet with a 61-80 numbered drill set (and a pin vise), when it all went pear shaped on me. I couldn't make any sense out of what was happening with the motor, since it was behaving like it was getting way more fuel than I was providing. It hit me a few days later; the drill bits were incorrect from the factory. I had drilled the jet out way too far.

I took each bit out and measured with a vernier, and discovered that of the 19 bits in the index, I only had six sizes (which were triplicated). I've learned to measure the bit before I happily drill away, so I don't unwittingly go too far.

I didn't think I'd have any success in filling a slow jet with solder. Since I had another virginal jet, I drilled it to the correct size (according to Mr.Vernier) and the motor was happy.

there are 2 types of "number drills'
one type is hole dia... the other
is hole area....

what type were you useing....???

moparrob · 12-24-2016, 06:04 PM

By the way - if anyone needs an extra 112 jet let me know because I have 2 of them I won't use. They would probably help wake up a stock bike or a bike with a pipe that lives at higher altitude. Free to the first 2 requests.

Merlin · 12-24-2016, 07:17 PM

Quote:

Originally Posted by moparrob

So the next likely problem would be the installed air injector emission control.I know there is a permanent way to block it off with a plate but does anyone know if you can temporarily disabled it by simply disconnecting and plugging the vacuum port and hose? I would like to isolate that as being a problem before I take any further measures. Thanks again for the input.

Yes that's not a problem. Iam doing the same thing myself.

moparrob · 12-25-2016, 12:23 AM

Cool, I will give that a try this week.

'16 TT250 · 12-25-2016, 01:08 AM

Quote:

Originally Posted by moparrob

does anyone know if you can temporarily disabled it by simply disconnecting and plugging the vacuum port and hose

The only way to guarantee it's not flowing is to seal off the connection. Nothing permanent or difficult, just put a cap on instead of the hose or something in the hose to seal it off. Not the little vacuum hose, the one at the head that actually feeds air to the port, this will eliminate all possibilities of air flowing into the exhaust. While I doubt that the air injection does anything to performance, I see the potential for it to rob some of the scavenging effect during valve overlap and change tuning effects; haven't tested the theory. If there was a plate installed where the gasket goes it would maximize the blocking of pulses a little more than a cap/plug on the hose fitting, but probably an unmeasurable difference. Ideally the air hole would be filled at the exhaust port so that it's not existent, but that's much more involved.

moparrob · 12-25-2016, 01:12 AM

Good point, I will take the extra precaution.

'16 TT250 · 12-25-2016, 01:14 AM

Quote:

Originally Posted by pete

there are 2 types of "number drills'
one type is hole dia... the other
is hole area.

Never heard of this. Do you have a link to some reference so I can read about it? The area would be hugely different than diameter and should be relatively easy to spot when looking at bits, but I'd like to learn about it.

'16 TT250 · 12-25-2016, 01:30 AM

Quote:

Originally Posted by moparrob

By the way - if anyone needs an extra 112 jet let me know because I have 2 of them I won't use. They would probably help wake up a stock bike or a bike with a pipe that lives at higher altitude. Free to the first 2 requests.

Very cool. I might, but I'll wait to see what I'm gonna do with mine.

Weldangrind · 12-28-2016, 06:12 PM

Quote:

Originally Posted by '16 TT250

Never heard of this. Do you have a link to some reference so I can read about it? The area would be hugely different than diameter and should be relatively easy to spot when looking at bits, but I'd like to learn about it.

X2. I was definitely using bits where the diameter was referenced, as confirmed by the vernier caliper.

EachAdventure · 12-28-2016, 08:57 PM

I am having a similar issue with mine. It has only happened twice, once yesterday morning and once this afternoon, and both times in the higher gears. I am practically at sea level so I highly doubt that jetting is the issue. Aside from the jetting, any idea what it could be?

'16 TT250 · 12-29-2016, 02:09 PM

I believe the stock bikes are jetted on the lean side for emissions. Being near sea level gives lots of air available and if it's cool where you are that'll add to even more available air (density) and might be enough to have you on the ragged edge of too lean.

2LZ · 12-29-2016, 03:20 PM

Quote:

Originally Posted by '16 TT250

I believe the stock bikes are jetted on the lean side for emissions.

Definitely. I've never seen a CB come other than totally leaned out. My neighbor's new TT250 isn't too bad...and we're at 3000'. We'll end up putting a Mikuni on it anyway, just for the jetting options.

Weldangrind · 12-31-2016, 06:00 PM

Quote:

Originally Posted by EachAdventure

I am having a similar issue with mine. It has only happened twice, once yesterday morning and once this afternoon, and both times in the higher gears. I am practically at sea level so I highly doubt that jetting is the issue. Aside from the jetting, any idea what it could be?

I'd throw a fatter main jet in; two steps larger should do the trick.

12-24-2016, 05:43 PM	#32
moparrob Join Date: Apr 2016 Posts: 79	I had a chance to do some more research on the issue and now believe the jetting changes I made are appropriate (117 Main). I have 2 identical bikes, a white one and a black one. The black one was the one that had the problem. I have since rejected the white one to be identical to the black one and it runs perfectly, without any hiccups. I have taken it on some sustained (indicated) 65 mph runs with no problems.This leads me to believe that the jetting is not the problem with the black bike which still hiccups. So the next likely problem would be the installed air injector emission control.I know there is a permanent way to block it off with a plate but does anyone know if you can temporarily disabled it by simply disconnecting and plugging the vacuum port and hose? I would like to isolate that as being a problem before I take any further measures. Thanks again for the input.
	0

12-24-2016, 06:04 PM	#34
moparrob Join Date: Apr 2016 Posts: 79	By the way - if anyone needs an extra 112 jet let me know because I have 2 of them I won't use. They would probably help wake up a stock bike or a bike with a pipe that lives at higher altitude. Free to the first 2 requests.
	0

12-25-2016, 12:23 AM	#36
moparrob Join Date: Apr 2016 Posts: 79	Cool, I will give that a try this week.
	0

12-25-2016, 01:12 AM	#38
moparrob Join Date: Apr 2016 Posts: 79	Good point, I will take the extra precaution.
	0

12-28-2016, 08:57 PM	#42
EachAdventure Join Date: May 2016 Posts: 16	I am having a similar issue with mine. It has only happened twice, once yesterday morning and once this afternoon, and both times in the higher gears. I am practically at sea level so I highly doubt that jetting is the issue. Aside from the jetting, any idea what it could be?
	0

12-29-2016, 02:09 PM	#43
'16 TT250 Join Date: May 2016 Location: Hacienda Heights, Ca Posts: 281	I believe the stock bikes are jetted on the lean side for emissions. Being near sea level gives lots of air available and if it's cool where you are that'll add to even more available air (density) and might be enough to have you on the ragged edge of too lean.
	0