Rejet issue

wheelbender6 · Post by **wheelbender6** » Thu Dec 27, 2018 8:29 pm

I was rejetting my wife's buddy 125 after adding a prima exhaust. Float bowl screws were stuck. Had to use an impact driver to loosen them.
-i couldn't go over 30 mph during the check ride. Inspected the carb and found the plastic cap on the top of it was cracked. That explains why the scoot would only do 30 mph (I hope).
-i plan to patch the crack with epoxy until I can get a replacement.

tenders · Post by **tenders** » Thu Dec 27, 2018 9:23 pm

Those screws on the Keihin carbs are a Japanese type of Phillips head called JIS that strip very easily with US Phillips screwdrivers. They're size M4 0.7 14mm (although a bit shorter might work as well), and you can get US Phillips replacements, or better yet - Allen head, that are very resistant to stripping - in stainless or high quality steel (marked 10.9, or 12.9) in the metric fastener drawer at Home Depot. I suggest a small dab of antiseize on the threads before reinstalling any fasteners like this into dissimilar metals, ie steel into aluminum.

I had some difficulty getting to higher speed after I reassembled my 4T carb a few weeks ago. Thought it was dirt in the main jet, but it turned out I hadn't gotten the gasket lined up correctly on the other side of the carb. So it was a vacuum leak. I'm not sure the plastic cap you're referring to is particularly functional, could you post a photo of it?

sc00ter · Post by **sc00ter** » Thu Dec 27, 2018 9:44 pm

Also make sure you didnt disconnect the accelerator pump spring. Thats what happened when I got my Buddy 125 back from the shop. Would not go over 30 mph. Had a chunk of blue latex glove caught on it.

Dooglas · Post by **Dooglas** » Fri Dec 28, 2018 6:09 pm

wheelbender6 wrote:I was rejetting my wife's buddy 125 after adding a prima exhaust. Float bowl screws were stuck. Had to use an impact driver to loosen them.
-i couldn't go over 30 mph during the check ride. Inspected the carb and found the plastic cap on the top of it was cracked. That explains why the scoot would only do 30 mph (I hope).
-i plan to patch the crack with epoxy until I can get a replacement.

Okay, I'll bite. Why swap to the Prima exhaust and invite all these problems? It really adds nothing to the performance of the 125 Buddy.

wheelbender6 · Post by **wheelbender6** » Fri Dec 28, 2018 8:50 pm

Thanks for the replies. The epoxy is applied and will need to set overnight. I'll check the accel pump and spring during assembly tomorrow.

wheelbender6 · Post by **wheelbender6** » Sun Dec 30, 2018 9:54 pm

After applying two coats of epoxy and letting it cure, I made the test ride today. My 125 still will not run over 30mph. It feels like the accelerator pump is inop.
-backfires a little on decel, even though I installed a larger jet.
-I made sure the accel spring was in place and the diagram looked good.
-I plan to remove and reinstall the related parts and to inspect for problems.
-I'll check the jet for a possible obstruction. After that. I'm out of ideas.
-Im working tomorrow, so I will resume on New Years.
Cheers

BuddyRaton · Post by **BuddyRaton** » Mon Dec 31, 2018 12:12 am

Dooglas wrote:
wheelbender6 wrote:I was rejetting my wife's buddy 125 after adding a prima exhaust. Float bowl screws were stuck. Had to use an impact driver to loosen them.
-i couldn't go over 30 mph during the check ride. Inspected the carb and found the plastic cap on the top of it was cracked. That explains why the scoot would only do 30 mph (I hope).
-i plan to patch the crack with epoxy until I can get a replacement.
Okay, I'll bite. Why swap to the Prima exhaust and invite all these problems? It really adds nothing to the performance of the 125 Buddy.

Unless you do the 161 kit, then it's worth it.

wheelbender6 · Post by **wheelbender6** » Mon Dec 31, 2018 1:47 am

"Okay, I'll bite. Why swap to the Prima exhaust and invite all these problems? It really adds nothing to the performance of the 125 Buddy."

I live 1000' from the Gulf of Mexico, which is great, but the stock exhaust rusts really bad. I hose off the scoot after rides, but there is still plenty of salt in the humid air.

k1dude · Post by **k1dude** » Mon Dec 31, 2018 4:20 am

It makes no sense that swapping out the exhaust would cause this problem. Are you sure it wasn't a recurring problem that progressively got worse with use and time?

Often you don't have to rejet when switching to a Prima pipe. The jet wouldn't cause the problem you're describing.

tenders · Post by **tenders** » Mon Dec 31, 2018 4:52 am

Doesnâ€™t sound like heâ€™s blaming the exhaust for the situation - heâ€™s blaming some disturbance in the carb after the rejetting. Not sure what else to say except to make sure the carb is carefully re-assembled.

What exactly did you do to the jets? Some of those aftermarket jets are chintzy, I would only use Keihin.

Do carb misadjustments cause backfiring? I tend to look at ignition/timing issues for that.

The exhaust could be a cause of these symptom if it were partially blocked. Seems unlikely unless the new exhaust is seriously defective.

wheelbender6 · Post by **wheelbender6** » Mon Dec 31, 2018 2:28 pm

I certainly don't blame the prima pipe. We have one on our other scoot.
-I think I caused the problem while rejetting.
-The 95 jet came from scooter works. I have run that same 95 jet in my other buddy 125 for a few years with no issues.
-i think the slight backfiring is caused by a lean fuel mixture.
-i have successfully installed jets before. This install was tougher because all the float bowl screws were stuck, and I used an impact driver. I must have damaged something on the carb or something is clogged.

wheelbender6 · Post by **wheelbender6** » Tue Jan 01, 2019 6:22 pm

I removed the float bowl today and ran a wire through all the jets and other passages but no clogs found.
-I removed the top cap of the carb to inspect the spring and diaphram. Everything looked good to this layman.
-I carefully reinstalled the parts and took a test ride. Results were the same. Runs good but will not go faster than 35mph.
-I will try again when the new top cap arrives.

babblefish · Post by **babblefish** » Tue Jan 01, 2019 8:03 pm

I had the same thing happen to me once. Try lubricating the sealing lip around the rubber diaphragm of the slider with some rubber safe grease then reassemble. Worked for me.

wheelbender6 · Post by **wheelbender6** » Tue Jan 01, 2019 8:56 pm

Thanks. I'll try some grease on the diaphragm this weekend. I have retired the wrenches for the day.

scootERIK · Post by **scootERIK** » Tue Jan 01, 2019 10:32 pm

wheelbender6 wrote:-I removed the top cap of the carb to inspect the spring and diaphram. Everything looked good to this layman.

Make sure you check in the folds of the diaphragm and around the "bottom" where it connects to the plastic part. It only take a small crack to make the scooter run poorly.

lovemysan · Post by **lovemysan** » Wed Jan 09, 2019 8:18 pm

wheelbender6 wrote:I removed the float bowl today and ran a wire through all the jets and other passages but no clogs found.
-I removed the top cap of the carb to inspect the spring and diaphram. Everything looked good to this layman.
-I carefully reinstalled the parts and took a test ride. Results were the same. Runs good but will not go faster than 35mph.
-I will try again when the new top cap arrives.

Is it running smooth? Does it break up or misfire?

I had this very thing happen. Poor running after a rejet. The airbox lid had deformed and it would not reseat causing it to suck too much air. I had to buy a used airbox lid to remedy it. Its very common for them to warp over time but usually they are fairly easy to get in properly.

wheelbender6 · Post by **wheelbender6** » Thu Jan 10, 2019 3:45 am

It runs smooth. Its just slow.
I didn't get to work on it last weekend because we had company. I'll give it a go this weekend.

vintagegarage · Post by **vintagegarage** » Thu Jan 10, 2019 1:43 pm

I'm also guessing that the diaphragm isn't seated properly. My buddy 150 accelerated smoothly but slower than a 50 and had a top speed of 40 BMPH until I got the diaphragm properly seated. Once I got the diaphragm properly seated, it accelerated like a rocket ship, with BMPH well over 65. Unlike scooter carbs where the throttle cable is attached directly to the throttle slide, the Buddy 125 carb requires full vacuum pressure to raise the throttle slide all the way up. If you have an air leak in the diaphragm area, or a slight fold in the diaphragm, the throttle slide will only partially lift, and you will be running with about 1/4 to 1/2 throttle, even when you have the right grip fully turned, and are expecting maximum power. With a leak or bind in the diaphragm area, the engine runs smoothly, idle is normal, but the scooter is slow to accelerate and has a slow top speed.

Here is a good video:
https://www.youtube.com/watch?v=wyspAHrMbb8

Stanza · Post by **Stanza** » Thu Jan 10, 2019 2:26 pm

vintagegarage wrote:I'm also guessing that the diaphragm isn't seated properly. My buddy 150 accelerated smoothly but slower than a 50 and had a top speed of 40 BMPH until I got the diaphragm properly seated. Once I got the diaphragm properly seated, it accelerated like a rocket ship, with BMPH well over 65. Unlike scooter carbs where the throttle cable is attached directly to the throttle slide, the Buddy 125 carb requires full vacuum pressure to raise the throttle slide all the way up. If you have an air leak in the diaphragm area, or a slight fold in the diaphragm, the throttle slide will only partially lift, and you will be running with about 1/4 to 1/2 throttle, even when you have the right grip fully turned, and are expecting maximum power. With a leak or bind in the diaphragm area, the engine runs smoothly, idle is normal, but the scooter is slow to accelerate and has a slow top speed.

Here is a good video:
https://www.youtube.com/watch?v=wyspAHrMbb8

wheelbender6 · Post by **wheelbender6** » Sat Jan 12, 2019 7:32 pm

wheelbender6 wrote:Thanks. I'll try some grease on the diaphragm this weekend. I have retired the wrenches for the day.

Ding Ding Ding! You da man babblefish. I put some grease on the edge of the rubber part and the scoot runs at full speed again.

I appreciate everybody's help.

babblefish · Post by **babblefish** » Sun Jan 13, 2019 6:14 am

wheelbender6 wrote:
wheelbender6 wrote:Thanks. I'll try some grease on the diaphragm this weekend. I have retired the wrenches for the day.
Ding Ding Ding! You da man babblefish. I put some grease on the edge of the rubber part and the scoot runs at full speed again.

I appreciate everybody's help.

Glad you got the problem solved. Good job!

Modern Buddy

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