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View Full Version : 83 250r running weird any thoughts?



seth6025
10-25-2016, 02:02 PM
Hi I just got the bike and I was wondering if you think I might have a carb issue or something else? I start the bike and let it warm up....It starts easy and idles fine. But when I take off there seems to be an issue. First though 3rd it wont rev out...it just kinda spits and sputters at the high rpm (or lack of) Then I hit 4th and it opens right up and so does 5th. I then gear down all the way and start over. All gears seem to open right up now.....If I shut it off this process starts all over again. Any ideas?

yaegerb
10-25-2016, 03:17 PM
Need some information first.
1. What model of carb is it? OEM or Aftermarket?
2. How many turns out is the airscrew?
3. What size is your pilot?
4. What clip is your needle on?

seth6025
10-25-2016, 03:22 PM
I just got it and I am actually taking the carb of tonight so I will post the results that I find. It is a mikuni carb and there is a number on the side that says 30 I believe. Don't think that is the correct carb for the year is it?

yaegerb
10-25-2016, 03:32 PM
Stock was Keihin, not Mikuni. However, if you find that it is a Keihin, then the stock carb specs for that model/year is the following:

Model: PE30A (30MM)
Float Level: 20MM
Air Screw Turns Out: 1-1/2
Needle Clip: 3rd from top
Pilot: 50
Main: 130

seth6025
10-25-2016, 03:35 PM
Awesome thanks I will compare that tonight....Also am I correct that a nice upgrade for my bike would be a Keihin 34mm PJ carburetor?

seth6025
10-25-2016, 06:07 PM
Ok so this is what it was...and yes it was a keihin carb

Model: PE30A (30MM)
Float Level: 20MM
Air Screw Turns Out: 3.5 turns out
Needle Clip: 2nd from top
Pilot: 50
Main: 130

I switched it to the above statement. About to try it out but one question on the air screw turns. Is one turn really a complete turn or just a turn with screw driver which would really kinda be half turn? I know kinda stupid question sorry lol

TwiZ
10-25-2016, 06:12 PM
One complete turn and half turn,or 3 half turns

seth6025
10-25-2016, 06:24 PM
ok thanks...it still seems to be doing it but I am gonna let it sit and try again because it will come out of it anyway after going through the gears. One more note is it has a FMF slipon but the expansion chamber looks original. And I have a makeshift air filter on it right now cause the old one fell apart when I touched it. It is still wraped in foam though. Would I need to make any other changes to carb to take into account the slipon? Also I am at sea level here

TwiZ
10-25-2016, 06:30 PM
Geeze...hope it hasnt been suckin in pieces of foam. Idk yaeger or the other guys here could be more helpful in that department. Be different if i was there i could have a better chance of helping dial it in

seth6025
10-25-2016, 06:35 PM
Don't think its sucked anything in....it still has the inside metal filter with the foam around it. I did just notice the plug wire was a little loose going onto the plug so I tightned that up and will try again....thank for the help and quick responses

seth6025
10-25-2016, 07:00 PM
nope no luck still doing it.......is the pj34 34mm a good upgrade?

TwiZ
10-25-2016, 07:48 PM
With the right mods probably. Gotta be careful,if you go to big your bottom end will suffer dramatically. With what you got going on i dont see you benefiting from a bigger carb. I could be wrong,not big on two smokers,but i know for sure a 4 stroke will be a boggy pig. You get it dialed in that things gonna rip

seth6025
10-25-2016, 08:05 PM
ok thanks for the input.....I will look into it further......one other question as I am new to 2 strokes, should it be smoking at idle or no....The way it is right now it don't smoke at idle and only a bit on throttle.....I can turn the air screw in a bit and it will smoke. Guess I just don't wanna be running too lean. I know my sled smokes like a bitc! but its a tripple

yaegerb
10-25-2016, 09:00 PM
So do you have the oem airbox and lid on? I would try and get this carb running right before investing in an upgrade. It should smoke some on idle and clear out when running down the road.

Have you checked for airleaks around the carb and intake boots?

seth6025
10-26-2016, 07:38 AM
Yes it has the oem airbox and lid on....there are a few small holes in the top of the airbox (maybe drilled or normal not sure) I have checked the boots for cracks and did not see any and the carb slides into them pretty tight. Its just weird that it does this and then comes out of it. Its not a huge deal but I know something is not right and that bugs me lol

seth6025
10-26-2016, 07:41 AM
I also pulled my new plug and it is a little black but not soaked or anything.

yaegerb
10-26-2016, 10:06 AM
Start the bike and while idling spray carb cleaner around the siphon mount joints on each bell of the carb (airbox to carb and carb to intake). Also, spray around the intake manifold where it bolts to the head. Listen for any increase in RPM's. If you hear them then you have a air leak on your intake track that needs to be addressed.

If this checks out then we have one more test to do. I think this final test will reveal the culprit (going from what you state in your original post).

seth6025
10-26-2016, 12:08 PM
Ok I will try that and let you know how I make out. Thanks

seth6025
10-26-2016, 12:13 PM
What is the final test if this does check out.....The suspense is killing me lol

yaegerb
10-26-2016, 01:09 PM
Final test will be a pressure test of the seals in the motor.

seth6025
10-26-2016, 02:45 PM
Oh ok. Will def need some guidance on that one if we come to it. I will be heading home soon to try the carb cleaner

yaegerb
10-26-2016, 03:16 PM
Oh ok. Will def need some guidance on that one if we come to it. I will be heading home soon to try the carb cleaner

Check out the pics in post #1 of the thread below.

http://www.3wheelerworld.com/showthread.php/181078-Pressure-test-250r-results-am-I-doing-it-right?highlight=pressure+test

Here's another good source of information on a pressure test.

http://www.klemmvintage.com/airleaks.htm

Essentially you will need an expandable plug (can be obtained from any auto parts store for a couple bucks) to plug off the exhaust. Then you will need to buy a pressure gauge and make the fitting to block off and check pressure on the intake side. Caution...use a bike tire pump or turn your regulator down to 1-5 PSI when pressurizing your motor or you can blow the seals.

Pressurize the motor to 6 PSI. The rule of thumb is the motor should hold 6 PSI for 6 minutes. If you notice ANY loss of pressure during that time.....

1. Get a spray bottle with a water/soap solution and start by ensuring that the sealing surface of your rubber plug and your "makeshift" pressure gauge/line are leak free. if not, re-tighten fittings.

2. If those are not leaking then you have a leak somewhere on your motor. Start spraying the solution around mating surfaces such as head to cylinder and cylinder to crankcase. If no bubbles are present then its time to soap down the seals of the motor.

3. The stator side is easy, just pull the left cover, remove the flywheel and soap down the seal and look for bubbles. If no bubbles are present there then its time to check the seal on the clutch side which is easy but a little messy.

4. Remove the clutch components and drive gear to reveal the clutch side seal and spray/check for bubbles.

By this point, I guarantee you will have found if a mating surface (typically gasket) or seal needs to be replaced.

Hope this helps

seth6025
10-26-2016, 03:49 PM
Great info, thanks

seth6025
10-26-2016, 04:46 PM
So no leaks sprayed around everything and it did not rev up....guess I have to make something for the pressure test

seth6025
10-26-2016, 05:41 PM
This is what my plug looked like after taking it for a drive. 236174

yaegerb
10-26-2016, 05:42 PM
This is what my plug looked like after taking it for a drive. 236174

Carb is running rich.

You could try moving your clip up 1 on your needle and see if that takes the "bog" out.

I would still pressure test at some point to ensure that you have no air leaks.

seth6025
10-26-2016, 05:45 PM
I can but that is where it was when I took it apart last night. The previous owner had it 2nd from top and I moved it to 3rd. It still worked the same both times

yaegerb
10-26-2016, 05:46 PM
I can but that is where it was when I took it apart last night. The previous owner had it 2nd from top and I moved it to 3rd. It still worked the same both times

ok, take it all the way to the top clip and see if it behaves differently. It should either get a lot worse or a lot better.

seth6025
10-26-2016, 05:47 PM
Ok will try that

seth6025
10-26-2016, 06:02 PM
Oh hell ya its allot better.....so what does that mean am I good? why would it be needed to be so far off the stock settings to work right?

yaegerb
10-26-2016, 07:47 PM
One of two things. Someone switched to a richer needle or more likely, the needle and needle jet are worn out and need to be replaced.

seth6025
10-27-2016, 06:31 AM
Ok for now should I adjust the air mix screw any different from the 1.5 turns out where I'm giving it less fuel?

yaegerb
10-27-2016, 09:53 AM
No, I would try to find a suitable replacement for that needle and needle jet. Are there numbers on that needle by chance?

seth6025
10-27-2016, 10:41 AM
Yeah I think there was something written on it I'm gonna pull it apart again and take another look

atc300r
10-27-2016, 11:58 AM
I would change crank seals just to be on the safe side.

seth6025
10-27-2016, 01:07 PM
Oh really would crank seals cause this kinda issue too

yaegerb
10-27-2016, 01:29 PM
Oh really would crank seals cause this kinda issue too

yes, that's why I told you to pressure test the motor....that test checks the crank seals.

seth6025
10-27-2016, 01:49 PM
Oh ok thanks. I will get something rigged up to check that

Ritz cracker
11-08-2016, 08:47 PM
I'm curious if you had a bad seal or not