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DerekM

Low Sound/Loss of power

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Been breaking in my LI150 with a BGM rt 195 kit, Ancillotti box exhaust and PHBL 25MM Carb. 

 

When running and warmed up cruising at about 3/4ths throttle in 3rd or 4th, the engine will backfire, and start to sputter. it will start back up, and run up to 1/4ths throttle making a low loud sound with no power behind it. any throttle beyond 1/4ths while riding makes the bike stammer like it is about to stall out. 

 

Swapped CDi's and still does this, both are new units, one blue one red. Stator is indian of known good working condition, and a new elemec flywheel. while this is occuring i hooked up a timing light and ensured my timing is set to 18 degrees and not jumping around. my jetting is 112 main, d22 needle, aq 264 and a 52 idle, which is close to where it needs to be however not fully tuned yet, with no plug chop, since i am still breaking the kit in.  a 115 is too rich and bogs the bike with this needle setup.

 

Is this an electrical or a jetting issue?

 

Video proof:

26525079506_96001824d5_b.jpg

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Sounds like fuel starvation.

Checked for gas tank cap not venting correctly and the fuel tap starting to go bad. Doesn't matter if the tap is new to you, it may still be an old tap and the rubber inside may be deteriorating.

 

More than likely the porting and flowing though. The gas has to flow through the ports correctly or all hell will break loose...

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The carb bowl is full when this happens. Waited it out over pho last weekend and returned after 30 minutes and the condition immediately returned. Drained the bowl, checked the float, refit the carb, and let it fill up the carb again and no change. Rode it home approximately 15 miles with 1/4 throttle.

I have not checked the tank cap.

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Is this a new issue or has this been this way since you got it running with current configuration...?

"99% of carb issues are electrical"

Backfires are due to lean or intermittent ignition issues.

Swap out the spark plug cap to the non thread use type... the type that clips on work best. I has a bike years ago that backfired and was very hard to get started due to the brass within the spark plug cap that worn away = weak or no spark

If it was a fuel flow issue then the rpm would go way up right before engine stopped firing. This looks like a electrical issue

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This has been a constant condition. I've misplaced my multi-meter in recent moves, and need to test both the stator and Cdi. I've been too busy to pick one up, but will do this.

Given that lean conditions can cause backfires I'm hesitant to continue causing this condition in case of improper jetting, but it may be necessary to get readings.

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Just get a cheapie multi meter from hardware store. The values you are looking for are listed in Sticky book.

That video seem to point to a lean condition. I had that exact thing when I was using a Dellorto with a bellmounth that was blocking one of the intake holes.

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It certainly could be electrical, so definitely check that, like the others said first. But to me, it seems to idle too smooth to be electrical. When I've had stator trouble, it's normally been intermittent spark, popping and bucking all over. And hard to start. Of course, that's not to say that it can't be electrical.

 

I'm gonna be the odd one and say it sounds like a rich condition to me. Fuel starvation in my experience has felt like surging and cutting in and out. It also looks like a lot of blowback, although its tough to tell. Is there a lot of smoke rolling out the exhaust? 1 simple test- turn your fuel tap off and rev it (gently) until the float bowl runs dry. If it starts to pick up and rev out just before it dies, I would look at over rich conditions. Also, You're only 1 jet size below complete flooding, so you still might be rich. And you seem to know the float bowl is full....maybe too full? Is there an adjustment for float height on the new Dell Ortos?

 

You could also create the condition, like in your video, then cut the engine dead and check the plug. That might tell you a bit of what's going on inside. And definitely try a new plug just in case it's that simple!

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When my Sil stator took a dump, it pretty much cut me off at a certain rpm and only when hot. I tested it, it failed and I rewired it with a bgm coil and trigger. It's worked great ever since.

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I had a engine 5 years ago that would idle fine but once rpm was increased missing and backfires would occur... my guru told me that unburnt mixture was being exploded at incorrect btdc timings.

Turned out it was a combination of old parts.... old worn out points and bad connection at sparkplug due to loose cap

Do the air leak spray test and do check behind stator for a leak too. Good luck

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So fuel starvation, lean condition, overly rich condition, or electrical issues. will do some more digging and report back.

thanks for making the diagnostic list larger everyone, not smaller.  :D

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Sounds like a lean condition but your jetting looks big.

 

For reference my RT195 (60/110)

 

PHBL24AS

60 choke

50 Pilot

98 main

D22 at 3rd clip up

40 Slide

UNI pod filter on a standard boot

 

Casa 185 (Colorado bike)

PHBL24

60 Choke

50 Pilot

95 Main (102 Open mouth)

D22 @ 3rd clip would hit a rev wall at 5k, switched to a D29 @ 2nd clip and would rev out to 7500 no problem

BGM mesh filter, no air scoop on a stock box

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Derek, is that a BD carburetor? Doen the hole at the carburetor mouth, the hole at 10 o'clock spot, go all the way to the choke?

The BD carburetors do.

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Might be the Float needle valve. I'm having a similar issue with mine. I thought it was the BGM stator, but after I swapped out the Flywheel, CDI, and stator, I still had the same issue. I also checked my fuel tap, because that has also caused a similar issue in the past (ethanol caused the rubber seal to deteriorate, impeding fuel flow). I think the Dellortos come with a 200 float needle valve, I read somewhere to try a larger one. Patrick at P-Town has my SX right now, he's going to install a 300 float needle valve. Another thing it could be is fuel frothing, I had that issue a few years ago with another scooter that had a very heavily ported top end.

 

I'm running a 225 top end with stage 4 porting, BGM big bore, BGM stator and Flywheel, and a 24mm PHBL

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My guess is way too rich, usually run a leaner needle, and raise the clip position to drop the needle even more, and usually have run a 90-102 main jet in the dllortos 24-25mm I've set up on 190's etc. Depending on the exhaust.

If it were starvation it would rev out faster before drying up.

Ohm the stator to rule out electronic pick up and LT coil

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I'm gonna be the odd one and say it sounds like a rich condition to me. 

Me too.. it almost sounds like your choke is on... but I'm sure it's not.. I'm in the too rich camp as well... and it does look like there's a lot of blowback.. at least it looks that way to me. 

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Thought about your vid but couldn't get it to play.... was wondering. Have you put the scoot in 1st gear yet to be sure engine isnt running backwards...? This happened to me once when I hooked up a cdi backwards. Was so strange. I let out clutch and I went in reverse. It sounded like your vid as timing was 180deg off

here's the flicker:

link:https://flic.kr/p/GpVY21

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After thinking this through a bit, and having no time to work on this issue at all....

Because the condition happens after 15-20 mins at 50-55mph and it needs to cool down all the way before it will run normal again I'm leaning towards heat causing something electrical to fail. Jetting would alter power in different throttle positions and would allow normal running after clearing the carb, which isn't the case here. It needs an hour or two before it will run normal again, not just empting the float bowl and then running it.

My wiring harness has the green kill from the loom hooked up to the Cdi, and the pink wire from the loom is running to the regulator for power. Purple and brown from the loom are not hooked up, and all stator wires are connected. Perhaps that might cause a power surge or overload on a CDI or stator? Or a ground issue?

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Heya Derek. I was having some intermitent issues before the jammy. I got a good condition indian stator to replace the indian stator that was in the bike for years and wala........so far so good since the jammy and i run ithe bike all the time. 

 

I forgot to add that mine was heat effected. I ended up finding some broken coil wafers that are between coil wire and steel cap. 

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Stator specs out fine. Scoot runs the same if all wires to the loom are disconnected, so I think this is not an electrical issue.

Ran the scoot, and the issue reappeared. While the issue was happening I tested the following one by one:

Lower main jet to 108

Dropped the needle jet to aq262

Removed wet dark brown plug, swapped with new

Removed gas cap

Dropped d22 needle to very top.

None of this changed the running condition. So I Dropped main jet to 102, engine dies past 3/4ths throttle.

Figured the engine was flooding so I kicked it clear and there was still no change.

At this point I'm stumped. I need to buy another carb for another bike so I'm going to swap carbs next. Any other thoughts?

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