Power loss

[BA80]

I remember you changing the cams and setting the timing but didn't see any mention of checking the chain. But if the cams are dead on the dots when #1 is at TDC that does sort of suggest that the chain is okay.

Ha ha ha..........this ain't my first rodeo.

[dbeardslee]

Ha ha ha..........this ain't my first rodeo.

Never doubted it. I figure at this stage, after all the stuff that you've checked, it doesn't hurt to spit out words to see where they'll splatter. Maybe something will click.

It does seem that you may be onto something with the needle position, but I agree with you - everything that happens has a cause. Just doing some spitballing to try and figure out what the cause was on this one.

[TopCatGr58]

I did a compression check a little bit ago and it's 115/105/105/115. No issue there.

Hey Greg,

I've stayed out of this for the most part because I'm not a REAL mechanic.

I just finished doing a quick NET search regarding LOW COMPRESSION on 4 stroke engines, symptoms and such.

Poor throttle response
Lack of power/acceleration
Increase fuel consumption.

And you said eariler that it's run fine for 40-50K miles....is that the total mileage of the engine, or is that just the miles you've put on it since you've gotten it or put it into service??

Here's a quote from www.dansmc.com site:

100 PSI is the minimum. It should be 125 to 150, and some engines have as high as 170 PSI or more. Yes, an engine can run with lower compression, but it will run very poorly. I've seen old, big, multi-cylinder outboards run with as little as 65 PSI and some lawnmowers run even less. However, for motorcycle engines 100 PSI is really on deaths doorway. Use your time to rebuild the engine, not to get another five or ten hours of life (maybe!) out of it.

SO.... it looks like to me that your compression levels are really a bit on the low side and from all you've done/tried, that it sounds like the engine is just wearing out! Post have been made in this thread fairly quickly, and so other REAL mechanics may have not seen your compression stats??

ANY INPUT from other mechs with regards to these comp levels probably contributing to the aforementioned symptoms since it seems like nothing else that he's tried has made any difference?

What's that phrase Sherlock liked to quote,

Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.

T.C.

[motoman]

Hey Greg,

I've stayed out of this for the most part because I'm not a REAL mechanic.

I just finished doing a quick NET search regarding LOW COMPRESSION on 4 stroke engines, symptoms and such.

Poor throttle response
Lack of power/acceleration
Increase fuel consumption.

And you said eariler that it's run fine for 40-50K miles....is that the total mileage of the engine, or is that just the miles you've put on it since you've gotten it or put it into service??

Here's a quote from www.dansmc.com site:



SO.... it looks like to me that your compression levels are really a bit on the low side and from all you've done/tried, that it sounds like the engine is just wearing out! Post have been made in this thread fairly quickly, and so other REAL mechanics may have not seen your compression stats??

ANY INPUT from other mechs with regards to these comp levels probably contributing to the aforementioned symptoms since it seems like nothing else that he's tried has made any difference?

What's that phrase Sherlock liked to quote,



T.C.

Good try T.C...........have to be REALLY low to have any effect on vacuum diaphrams OR venturi velocity though.

[bikerphil]

I would try advancing the timing until it pings, then back it off a little. Definitely that will give the bike more pep. You might lose that midrange bog, who knows.

[BA80]

Hey Greg,

I've stayed out of this for the most part because I'm not a REAL mechanic.

I just finished doing a quick NET search regarding LOW COMPRESSION on 4 stroke engines, symptoms and such.

Poor throttle response
Lack of power/acceleration
Increase fuel consumption.

And you said eariler that it's run fine for 40-50K miles....is that the total mileage of the engine, or is that just the miles you've put on it since you've gotten it or put it into service??

Here's a quote from www.dansmc.com site:



SO.... it looks like to me that your compression levels are really a bit on the low side and from all you've done/tried, that it sounds like the engine is just wearing out! Post have been made in this thread fairly quickly, and so other REAL mechanics may have not seen your compression stats??

ANY INPUT from other mechs with regards to these comp levels probably contributing to the aforementioned symptoms since it seems like nothing else that he's tried has made any difference?

What's that phrase Sherlock liked to quote,



T.C.

You may be right TC. I had no idea of the condition of this engine when I slapped it in there 5 years ago out of a parts bike.

It seems to me that an engine that's headed south would use more than a quart/quart 1/2 between oil changes though. That's all this one uses. And, it seems that the fuel demands would head to the richer side rather than leaner.

The compression guage I used is kinda iffy too, as far as accuracy of readings goes. The fact they were all very close seems to indicate there isn't an issue there. I will recheck that with a better tool though. Thanks.

I would try advancing the timing until it pings, then back it off a little. Definitely that will give the bike more pep. You might lose that midrange bog, who knows.

I already have the base timing at 10 degrees with the E centrifugal advance.

[MPittma100]

Power Loss

Hi Greg,

You mentioned that you have replaced the pick up coils. Did you splice them in to the existing harness or replace them as an assembly? JAT

[BA80]

Hi Greg,

You mentioned that you have replaced the pick up coils. Did you splice them in to the existing harness or replace them as an assembly? JAT

The whole assembly Mike. Breaker plate and all right up to the plug behind the fuse panel.

[ViperRon]

AS to TC question about compression I had my rings burnt up and compression was terrible some 60 and 90 numbers and it did not act like the video I saw. I did have a pick up go bad one time and it would drop 2 cylinders and then pick them up again and it was sorta like what Greg had but the cylinders would come and go and also Greg swapped out the coils you could also tell it lost 2 cylinders and it would not idle. I did have a rust issue in the tank once and it clogged my filters and it acted like this but he has checked fuel lines. So I am lost as to what it is.

[BA80]

This has got me totally confused Ron. I'm going to try leaning out the main system some more today, it seems to like that.

Still, something has to have caused it to change it's fuel demand and that has me stumped. The only thing I've changed during this process is putting the pods on to make the carbs easier to remove. And that should have made it want MORE fuel.

[CaptonZap]

This has got me totally confused Ron. I'm going to try leaning out the main system some more today, it seems to like that.

Still, something has to have caused it to change it's fuel demand and that has me stumped. The only thing I've changed during this process is putting the pods on to make the carbs easier to remove. And that should have made it want MORE fuel.

Lemme see if I have this right.
You ride this engine for umpteen thousand miles, take the valve cover off, and "If you BOTH will read back to the beginning of this thread you'll see that I went to check valve clearances an found some damage to the cam lobes (pics included) and I actually changed out the cams."

You put it back together, it doesn't run right, and you start in on carbs and ignition. Come on Greg, you are smarter than that. The one thing (if I read this right) that you changed was the cams, and you think something else is causing the problem.
In my book, I would go back and take a good look at the cams. Part numbers, wear patterns on lobes, lobe profile compared to take out cam, cam timing, etc.
Or, keep messing with the carbs.

CZ

[BA80]

Lemme see if I have this right.
You ride this engine for umpteen thousand miles, take the valve cover off, and "If you BOTH will read back to the beginning of this thread you'll see that I went to check valve clearances an found some damage to the cam lobes (pics included) and I actually changed out the cams."

You put it back together, it doesn't run right, and you start in on carbs and ignition. Come on Greg, you are smarter than that. The one thing (if I read this right) that you changed was the cams, and you think something else is causing the problem.
In my book, I would go back and take a good look at the cams. Part numbers, wear patterns on lobes, lobe profile compared to take out cam, cam timing, etc.
Or, keep messing with the carbs.

CZ

Ok CZ, get this right. My engine is a 2H7 021137 (79 F) , the engine the cams came out of is a 2H7 001904 (78 E). If you look them both up in the parts fiche you'll notice that they BOTH take EXACTLY THE SAME cams.

The cams in my engine were fine when I put it in. This ISN'T my first time under the valve cover.

Instead of feeble attempts to insult my intelligence how about a valid attempt to solve the question?

[stereomind]

Put your jets back how they were, put all the old parts back on, find someone with a dyno and an EGA perhaps.. and spend days figuring out what happened, or just make it run right as it is and deal with it later if it decides to go back to its old gas hog ways... It's not like you don't have a spare mill or two....

[BA80]

It never was really a "gas hog" Vlad, except maybe these last couple of trips.

Right now I'm running 1 size smaller pilots and 1 step leaner on the needles than I have been running for the last few years.

[stereomind]

For what it's worth, my Venturer is still running rich. I get about 32mpg if I don't get too crazy with the throttle, but I can tell I'm burning way more fuel than I need to. I mic'd the emulsion tubes and needles.. Running stock jet sizes. I might have to hit you up for some smaller jets too! lol