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Vespa px125
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Vespa px125
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Hi I'm new to the group and need some advice I've just had a bgm 177 kit fitted on my px125 I've got 24/24 carb with 55/160 idle jet and be3 and 120 mj fitted with sip3 exhaust but struggling with a tick over either to fast or none.
What setup should I be looking at to help get started.

Thanks for any help
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Molto Verboso
One or two fun scoots....nothing too precious
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Posts: 1984
Location: UK (South East)
 
Molto Verboso
One or two fun scoots....nothing too precious
Joined: UTC
Posts: 1984
Location: UK (South East)
UTC quote
I had a very similar setup a few years ago. A richer idle is standard practice, in my case 52/140 if memory serves. However, there are a number of other factors. Did you simply install the BGM kit onto an otherwise standard and well running engine, or was a broader engine rebuild and porting involved?
OP
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Lurker
Vespa px125
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Lurker
Vespa px125
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UTC quote
It had a Malossi 166 before never skipped a beat changed to the bgm 177 now it's just not running right properly
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Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
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Lucky
@chandlerman avatar
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UTC quote
Mark w wrote:
It had a Malossi 166 before never skipped a beat changed to the bgm 177 now it's just not running right properly
I have (and have had) multiple BGM177 builds and if set up right, they can be absolute beasts.

Coincidentally, about a year ago I went from a Malossi 166 to a BGM 177 on one of my motors. I'm getting 17 HP on that build with a 60mm crank, SIP RoadXL, and running SprintV cases with a 190 intake duration.

(I had to re-do the jetting, of course, but assuming you removed the transfer gates, the porting on the BGM, the Malossi 166, and the Polini 177 are all pretty similar. Add a little bit of Dremel work and the BGM uses Polini base spacers nicely.)

That being said, I strongly suspect it's going to be port timing. Based on experiments with another bike, the BGM's performance falls of really quickly if the port timings are too high.

Do you have any base gaskets on the cylinder? What's your crank? Is the inlet stock? Do you know for certain that ignition timing is at 18 BTDC?

Lastly, what exhaust are you running? Is it a box or a tuned pipe?

Performance parts are not nearly as plug n' play as the parts houses would have you believe, but nothing that can't be overcome.
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Molto Verboso
1958 Allstate 177VMC, 1962 Allstate, Yamaha Vino 70cc
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Posts: 1994
Location: Philadelphia
 
Molto Verboso
1958 Allstate 177VMC, 1962 Allstate, Yamaha Vino 70cc
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Posts: 1994
Location: Philadelphia
UTC quote
First- Has it passed a pressure test?
OP
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Lurker
Vespa px125
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Vespa px125
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UTC quote
Yes it's had a pressure test fine carbs tightened right.
It's got a sip3 box exhaust unfortunately I've given up and sending it in to get sorted out it's beat me
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Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
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Location: London UK
 
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: UTC
Posts: 4605
Location: London UK
UTC quote
Mark w wrote:
Yes it's had a pressure test fine carbs tightened right.
It's got a sip3 box exhaust unfortunately I've given up and sending it in to get sorted out it's beat me
If you block the carb inlet does it stop?

if yes, check the very tip of the pilot jet. Tiny hole that blocks easily.
@chandlerman avatar
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Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
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Location: Nashville

78 Days Since Last Explosion
 
Lucky
@chandlerman avatar
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9979
Location: Nashville

78 Days Since Last Explosion
UTC quote
Mark w wrote:
Yes it's had a pressure test fine carbs tightened right.
It's got a sip3 box exhaust unfortunately I've given up and sending it in to get sorted out it's beat me
Pressure test passed is always good.

You should see 12-13 HP with that setup and a SIP Road 3. So on par with a P200. Gotta make sure the port timings are down in the 123-124 TD range, though. I'm going to guess they're too high, so you lose all the torque.
UTC

Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: UTC
Posts: 4605
Location: London UK
 
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: UTC
Posts: 4605
Location: London UK
UTC quote
chandlerman wrote:
Pressure test passed is always good.

You should see 12-13 HP with that setup and a SIP Road 3. So on par with a P200. Gotta make sure the port timings are down in the 123-124 TD range, though. I'm going to guess they're too high, so you lose all the torque.
Surely BGM TD timing is nowhere near that high on a 57mm crank. Not such a vanilla kit if going over 124, with a stock crank.
@chandlerman avatar
UTC

Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9979
Location: Nashville

78 Days Since Last Explosion
 
Lucky
@chandlerman avatar
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9979
Location: Nashville

78 Days Since Last Explosion
UTC quote
Jack221 wrote:
Surely BGM TD timing is nowhere near that high on a 57mm crank. Not such a vanilla kit if going over 124, with a stock crank.
Good point. I didn't think about long stroke vs. stock. OP, ignore my timing advice.
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