Loss of power at certain RPM

[The_big_dill]

Hi all,

Recently, i have noticed that when i hit about 4-5k RPM there is very little power in the bike... feels somewhat like running low on gas.

When i get to about 6-7k RPM the power kicks in and gets me going.

The bike just rolled over 40,000 KM. Carbs have been cleaned at the beginning of the season, however i know i need to synchronize them.

I have a feeling the valves may need reseatting, what do you guys think?

Thanks,

Phil.

[Lychee]

Are you sure the power loss is related to RPM and not to throttle position?

[The_big_dill]

Originally Posted by Lychee

Are you sure the power loss is related to RPM and not to throttle position?

Well, if i go WOT it isn't very responsive at 4-5k, but once i pass that range its a lot more responsive.

And what would poor throttle point to?

I also want to mention that someone pointed out to me that my valves are loud and i did notice that they are clapping louder than usual. I do not know of the history of this bike, owned it since 37,000 km.

[Lychee]

Originally Posted by The_big_dill

Well, if i go WOT it isn't very responsive at 4-5k, but once i pass that range its a lot more responsive.

And what would poor throttle point to?

I also want to mention that someone pointed out to me that my valves are loud and i did notice that they are clapping louder than usual. I do not know of the history of this bike, owned it since 37,000 km.

I had a bog at 4k-5k before that ended up being too many washers under the needles... But it was really related to throttle position and my bike was reaching 4-5k during a my roll on.

Poor response to throttle position would point to the carburetor.

You can eliminate the valves as a starting point if you like, but generally valves out of adjustment would give you low rpm issues such as odd idles and hard to start in the morning situations. I've also thought that the valves get quieter when they are getting out of adjustment, since the ideal adjustment is toward the looser (and louder) end of the spectrum.

[The_big_dill]

Originally Posted by Lychee

I had a bog at 4k-5k before that ended up being too many washers under the needles... But it was really related to throttle position and my bike was reaching 4-5k during a my roll on.

Poor response to throttle position would point to the carburetor.

You can eliminate the valves as a starting point if you like, but generally valves out of adjustment would give you low rpm issues such as odd idles and hard to start in the morning situations. I've also thought that the valves get quieter when they are getting out of adjustment, since the ideal adjustment is toward the looser (and louder) end of the spectrum.

The idle is bad, but i have no trouble starting. Sometimes i start with half a second on the crank on a cold engine.

The way i understand it is that valves get louder from carbon build up, and they become "sticky".

I have never touched the needle shims in the carb... and it was find before.

[Lychee]

Originally Posted by The_big_dill

The idle is bad, but i have no trouble starting. Sometimes i start with half a second on the crank on a cold engine.

The way i understand it is that valves get louder from carbon build up, and they become "sticky".

I have never touched the needle shims in the carb... and it was find before.

I thought the noise came from the increased distance traveled by the valve stem (hammer) to meet the rocker (anvil).

[FvnnyL3tt3r1ng]

Surprised nobody has mentioned the main jets being clogged. It's probably the most probable scenario and it is definitely the first thing I would look at. Might as well plan a carb clean.

[Lychee]

Originally Posted by FvnnyL3tt3r1ng

Surprised nobody has mentioned the main jets being clogged. It's probably the most probable scenario and it is definitely the first thing I would look at. Might as well plan a carb clean.

He said carbs were cleaned recently and that he had plenty of power up top. Do you still think main jets?

[FvnnyL3tt3r1ng]

Originally Posted by Lychee

He said carbs were cleaned recently and that he had plenty of power up top. Do you still think main jets?

Yeah, I'd take a guess and say higher air flow could be why there is power up top but not in the mid range....

[xaple]

I had this problem and it turned out to be water in the bowls

[The_big_dill]

Originally Posted by xaple

I had this problem and it turned out to be water in the bowls

I hope its just a carb clean

Will get back when i figure it out

[KELPHYN]

Sounds like dirty carb. 4-5000rpm is around where the carb starts switching circuits(low speed to high speed) If it is a problem that has just started I would suspect a clogged passage in carb. I would try some carb cleaner in the gas first and go out and run it hard for half tank if you can. Hopefully that will clean it out. Check you plugs and air filter too.

[choneofakind]

I'm betting it's not main jets.

Is there damage to any of the slides or diaphragms inside the carburetors?

[The_big_dill]

Originally Posted by choneofakind

I'm betting it's not main jets.

Is there damage to any of the slides or diaphragms inside the carburetors?

How can damage occur?

I have not really touched the carbs since the rebuild months ago and this problem only appeared now.

[FvnnyL3tt3r1ng]

Have you installed a new fuel filter recently?

[choneofakind]

Plastic and rubber parts crack and rot over time. It's also possible that the lip of the diaphragm was kinked or something when you it back in the carb. This can cause creases, which wear.

I'm just suggesting things to look for, that's all.

[The_big_dill]

Originally Posted by choneofakind

Plastic and rubber parts crack and rot over time. It's also possible that the lip of the diaphragm was kinked or something when you it back in the carb. This can cause creases, which wear.

I'm just suggesting things to look for, that's all.

And i appreciate your suggestions

I have no fuel filter on the bike.

[FvnnyL3tt3r1ng]

Originally Posted by The_big_dill

I have no fuel filter on the bike.

No fuel filter as in you removed the OEM one???? If thats the case then you're letting anything that can get past the screens in your gas tank in the carbs. It takes the smallest flake to completely clog one jet and take out the cylinder...

[The_big_dill]

Originally Posted by FvnnyL3tt3r1ng

No fuel filter as in you removed the OEM one???? If thats the case then you're letting anything that can get past the screens in your gas tank in the carbs. It takes the smallest flake to completely clog one jet and take out the cylinder...

Well for one thing, this bike never came with a fuel filter. Furthermore, if it clogs the carb, it can't take out a cylinder...

[FvnnyL3tt3r1ng]

It takes out the power to that cylinder. Aren't you the one asking for help? Good luck Dill pickle

[BlueRaven]

We're supposed to helping one another not insulting. I can't find any evidence that Dill's bike has a fuel filter.

[The_big_dill]

Originally Posted by BlueRaven

We're supposed to helping one another not insulting. I can't find any evidence that Dill's bike has a fuel filter.

From what i have read, these bikes don't come with fuel filters. I may be wrong, but i heard people put them on optionally. I think its a good idea, just never got around to finding an appropriate filter for the hose sizes i have locally.

@FunnyLettering, i didn't mean to offend you, i tend to over do the periods at the end of a sentence, trying to fix that habit :P