350x power lag at top end

[Shawn Powell]

So I adjusted my valves and engine starts easy and doesn't make any crazy noise like I'm too loose , and now it bogs bad at top end. I also installed my new SupertrApp muffler and I'm at 14 discs so I doubt it could be that. Any ideas?


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[Ranvier]

Shawn you probably can tune a carb a lot better than me but I would take off a couple discs or increase the main jet?

[yaegerb]

Next time it bogs at top end reach over and pull on the choke and see if the bog goes away.

[Shawn Powell]

Shawn you probably can tune a carb a lot better than me but I would take off a couple discs or increase the main jet?

It seems to rich but I'm only at 142 main jet. Falls right on its face at hard throttle. I can't see a 14disc SupertrApp being that much more restrictive. I'm wondering if it could be valves? I'm gonna re check those and maybe swap my old DG back on for a test drive. And thanks for the confidence in my carb tuning lol. Wish I believed in me that much haha


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[Ranvier]

I'm at 140 main with 12 discs at 2500 feet. I recheck valve clearance as soon as a new plug doesn't fix hard starting. The choke and airbox lid tests are quick and easy checks. Did you repack the supertrapp?

[Shawn Powell]

I'm at 140 main with 12 discs at 2500 feet. I recheck valve clearance as soon as a new plug doesn't fix hard starting. The choke and airbox lid tests are quick and easy checks. Did you repack the supertrapp?

It's brand new. Have no air box lid, custom aluminum one no snorkel. Starts great. I'm about 800ft home elevation. Gonna check valves again. And swap out mufflers see what happens.


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[knappyfeet]

Assuming it ran fine before..........what changed since then?

Did you look at the spark plug?

[Shawn Powell]

Assuming it ran fine before..........what changed since then?

Did you look at the spark plug?

I added a dual oil cooler , so I had to take off my valve cover so I had to re adjust my valves, and I swapped my DG exhaust for a SupertrApp.


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[Scootertrash]

What about starting at square 1 as far as jetting instead of guessing?

[Shawn Powell]

What about starting at square 1 as far as jetting instead of guessing?

My jetting isn't that far out, a 142 with no air box lid a k and n and a SupertrApp muffler, I guess my question was more if my valves sound ok and bike starts easy could they be out to where it had zero power from mid to top end? But yeah I'm gonna re check clearances if there ok swap my old muffler on and test drive it.


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[yaegerb]

valve clearances wouldn't make you bog at full throttle. Clearances don't magically change with RPM. Its jetting, do what I said above with your choke. If it doesn't bog anymore its lean, if it still bogs or gets worse its rich. Change main jet accordingly.

[knappyfeet]

My jetting isn't that far out, a 142 But yeah I'm gonna re check clearances if there ok swap my old muffler on and test drive it.

I think your jetting is fine.

Your thinking is perfect on this. I would change out the exhaust for the DG to see if it improves anything.

My niece lives in Apple Valley so when they check and adjust anything they just go out and test it right there! If I did that here the police would be called.

On a side note....I started a thread on a different forum kinda comparing k&n pods with other cheaper pods for multi cylinder street bikes (older ones) and one guy on there ran all kinds of dyno numbers. On thing that was noted was the difference (leaning effect) with muffler vs no muffler. The point? It doesn't take much to alter the performance in a negative way with a combination of exhaust or intake variations. I'm not saying you did though........it just got me thinking of the exhaust change.



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[Shawn Powell]

I think your jetting is fine.

Your thinking is perfect on this. I would change out the exhaust for the DG to see if it improves anything.

My niece lives in Apple Valley so when they check and adjust anything they just go out and test it right there! If I did that here the police would be called.

On a side note....I started a thread on a different forum kinda comparing k&n pods with other cheaper pods for multi cylinder street bikes (older ones) and one guy on there ran all kinds of dyno numbers. On thing that was noted was the difference (leaning effect) with muffler vs no muffler. The point? It doesn't take much to alter the performance in a negative way with a combination of exhaust or intake variations. I'm not saying you did though........it just got me thinking of the exhaust change.



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I should also say it's a 142 in a 400ex carb , so it gets more fuel than factory via accelerator pump. But it ran perfect with that pos DG muffler on it. Just ungodly loud lol. I guess if my valves check out ok I'll swap mufflers and see what the heck happened. Maybe I'll have to drop a jet.


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[Shawn Powell]

So an update but maybe no solution, all signs point to to much fuel, checked a re adjusted my valves. I was out maybe .001 on one of the four, so I don't think that was an issue. I was a bit tight on my plug. Barely but like .002. So I dropped a jet from 142 to a 135 ( couldn't find my 138 for some reason) but ran out of time to test drive it. I'll see tomorrow how she goes. I did speak with some exhaust guys and they said even if I run 20 plates on my SupertrApp I'm still having more back pressure than that straight through DG.


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[Shawn Powell]

So I still have no power at top end after dropping a jet and then I swapped my old DG back on. Is there any way I adjusted the valves on the wrong stroke? If my timing mark is on the notch can I be 180 out? I checked and the piston was all the way up! Can it be on the exhaust stroke and still be on the t mark? I'm so lost at the moment. Starts fine and seems to have power at bottom but loses it about half throttle to top. Like it's mad flooded but before I did this oil cooler it ran fine on these settings. HELP PLEASE lol


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[atc007]

Your valves are fine. You are paying for mistakes, we must learn from them. You simply need to jet for the new exhaust,,or,,start troubleshooting. How does your plug look? It tells you everything about what is going on inside. If it looks great and choke when warm,chokes you out,,I doubt it,,,,you're good. If choke helps, you're lean. I highly suspect you simply need to clean your carb and or jet. I have seen 50 times over the years,a perfectly running bike goes in the shop,and backs out the door with a completely new/unrelated problem! It is frustrating and needs troubleshooting. A bad CDI,loose ground will do exactly what you are describing. I suspect you very simply have a tiny piece of debris in your carb/or a jetting issue. Your valves are fine.

[yaegerb]

Your valves are fine. You are paying for mistakes, we must learn from them. You simply need to jet for the new exhaust,,or,,start troubleshooting. How does your plug look? It tells you everything about what is going on inside. If it looks great and choke when warm,chokes you out,,I doubt it,,,,you're good. If choke helps, you're lean. I highly suspect you simply need to clean your carb and or jet. I have seen 50 times over the years,a perfectly running bike goes in the shop,and backs out the door with a completely new/unrelated problem! It is frustrating and needs troubleshooting. A bad CDI,loose ground will do exactly what you are describing. I suspect you very simply have a tiny piece of debris in your carb/or a jetting issue. Your valves are fine.

Thank you, I was tired of saying he same thing over and over.

[Shawn Powell]

I did all that. Zero change. I swapped my old DG back on. Zero change. It ran fine before I took it all apart. Even removed my whole air filter. Zero change. It's not jetting. I'll check the grounds and swap the CDI. See what happens.


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[Mickey Dunlap]

Your cam timing is off a tooth.

[Shawn Powell]

So she lives AGAIN!! Somehow when I put my valve cover back on I must have bumped the engine over or I was 180 degrees out or something ( I'm not that smart guys) so today I basically tore it back down to square one , valve cover off , right side crank case cover off , start over. Thanks to Mickey Dunlap for answering my email question and pointing out to me if I'm off a degree or two this would be an issue. And thanks to everyone else for chiming in knappy Yaegerb glamy atc007 ranvier scootertrash and anyone else I missed. I'll bring everyone beers if imperial invasion happens again next season. I truly appreciate the love fellas. I'll be at pismo beach either next weekend or the weekend after( depends on work) Thanks again!!


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[Shawn Powell]

So still not quite rite I'm thinking now it's to rich. Need to warm it up though. Gonna try the stock 138 jet and test.... got worse with choke on


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[Rob Canadian]

Just for giggles. See how the supply (gas) goes to the carb. flow wise. Pop the fuel line off the carb. Put it in a jar if possible then open the petcock.
Watch the flow.

Simple test. This is the first thing I do. Rules out fuel cap, petcock obstruction and fuel line to the carb.