SuzukiSavage.com - Lack of Power at Top End after Mods

Clark Zellmer

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Lack of Power at Top End after Mods
06/19/05 at 15:01:21

I have been doing some of the suggested mods on my savage to increase power. It worked for a time, but my latest changes seem to be stepping backwards. I thought I'd ask for help and ideas before I start ripping it back apart.

Stock: Backfire and lack of power, top speed 70mph

Mod 1) 1/2 spacer and Idle Mix screw adjust: result most of back fire gone.

Mod 2) No spacer and 152.5 main jet: backfire 99% gone and much more power, top speed 85+mph

Mod 3) K&N replacement filter, snorkle removed: some backfire returns

Mod 4) Harley Sportser Muffler, 155 main jet, iridium spark plug: Sounds great, no backfire, lack of power beyond mid range, top speed 60mph

Mod 5) 152.5 main jet: Slightly better top end but still bad, top speed 70mph,

I am ready to take the Sportster muffler back off just to make it have top end power again, but I dont' think that is the real problem.

Help!

Clark

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red2k1

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Re: Lack of Power at Top End after Mods
Reply #1 - 06/19/05 at 17:21:25

Well, it seems to me that you had a problem straight out of the box with a top speed of only 70 mph. That seems a little unusually low to me.

In any case, what year is the bike, how many miles, etc.? Does it have a fuel filter on it? When you took apart the carb, how did the slide assembly look?

Just taking a shot, check the vacuum line that runs from the carb to the fuel valve on the gas tank. Check to see that there are no holes and the like in the line. Better yet, just repalce it for 57 cents.

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Clark

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Re: Lack of Power at Top End after Mods
Reply #2 - 06/19/05 at 19:53:23

It is a 2001 with 3,500 miles on it. I bought it used this spring with 2,500 miles. It was in great shape and very stock. It was obvious that not a single screw or bolt had been removed.

I will check the vacuum hose tomorrow and the slider/diaphragm as well. They are in good shape, but I may not have gotten the spring in straight, or the hose may be kinked.

I took it out again this evening and there is no increase in engine speed after the throttle is 2/3 open. From 2/3rds to full throttle it actually looses power and does not gain speed. I could only get up to 69MPH on the 5 mile stretch of interstate. No power to even pass a 1979 Ford Pinto.

Clark

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WD

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Re: Lack of Power at Top End after Mods
Reply #3 - 06/19/05 at 22:40:30

Definitely something amiss. Minw with an open exhaust, stock dirty aircleaner and stock jets would hit 100 mph with no problems, other than the pipe turning cherry red (WAY too lean). I recently repacked the muffler (waste of time, lasted 3 days), and top end was considerably lower, almost as pathetic as the stock muffler. I'd suggest deleting your airbox door, with a bigger jet, you may be running too rich now. These bikes make better speed running ultra lean. An open pipe should help the top end at the expense of low end torque, NOT the other way around.
-WD

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Reelthing

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Re: Lack of Power at Top End after Mods
Reply #4 - 06/20/05 at 03:54:00

If it sounds great we can assume the muffler isn't clogged up with a dirt dobber nest!

what spring are you talking of ? - the diaphram spring? - be real sure it's in correct seated in the dish in the cover , the rubber edge in the grove and the tab lined up perfect - you might want to check that diaphram for any tears or dirt on the slide - if it's up ward movement is not free(dirt) or proper (tear or hole) it sure could produce this situation as in can't pull the needle out and open up the main jet - and be ceatain the needle jet tube is seated properly - the main jet screws into the bottom and holds it in - but if you push on the main jet when installing it you may can unseat it - I'd think this is the area to focus on.

After a cup of coffee - yep I'd bet if the spring wasn't seat properly and laying across the diaphram it would do this exactly - it would block the upward movement and not open the mainjet - which is what you need at 2/3 up throttle.

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Savage_Rob Serious Thumper Alliance Member Offline Mechanically Inclined Amateur Posts: 6972 Texas (Dallas area) Gender:	Re: Lack of Power at Top End after Mods Reply #5 - 06/20/05 at 09:52:34 Yeah, there's definitely something amiss. I'm now running a 55 pilot jet and a 152.5 main jet with my MAC installed and she's running pretty sweet right now. I was doing 70-75 in the HOV lane on the way in to work this AM and she definitely had power to spare.
Back to top	1998\|MAC muffler\|ceramic coated header\|K&N air filter\|Amal Mk2 carb\|Odyssey battery\|iridium plug\|NC windshield\|Dunlop 491s\|Superbrace\|EBC brake rotor\|12.5" Progressive shocks\|Kuryakyn ISO grips IP Logged

Dingo_Jones

Ex Member

Re: Lack of Power at Top End after Mods
Reply #6 - 06/20/05 at 11:30:12

I was going to post this in a new topic, still might, but here's my recent experience with the sportster muffler.

I've had my savage a few months now, put a little over 4000 miles on it, averaging a bit over 1,000/month with commuting and pleasure rides.
Top speed I've reached at completely stock was 92 on an open highway.
Last weekend on a trip back to seattle from portland, crusing at a solid 80-85 most of the way, I managed to blow a weak rusty rivet out of the muffler, ended up as a hole about the size of a dime. I'd been thinking about the sportster muffler, and had one laying around the garage, so I went ahead and threw it on there with some help of that terrific walkthrough.
I'm not getting any leakage, and the muffler sounds terrific. Deffinately a different bike at the low end. No more fart on shutoff, ect.
However... I can't get above 80 without feeling very uncomfortable. The bike seems generally uncomfortable about anything above 78, and begins to take on a nice vibrational shake at around 82-83. It almost feels like it's being restricted....
Anyhow, aside from that huge drop in the top end, I love the new muffler.
Any thoughts?

-DJ

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rkutzner

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Re: Lack of Power at Top End after Mods
Reply #7 - 06/20/05 at 17:41:59

My guesses:

Mod 1: You richened up the bottom and mid, it ran better.

Mod 2: You richened up the mid and top end, ran even better. Totally removing the spacer is a no-no (some have experienced raw feul dump at lower rpms), though, you should at least put in 1 or 2 #4 washers.

Mod 3: You leaned it out some, some backfire returns, probably when you are getting off the throttle.

Mods 4 and 5: Gets confusing here because you made the number 1 mistake when modifying (or troubleshooting) ANYTHING. Only 1 change at a time, it will always save you time in the long run. My guess is the muffler may have leaned the bottom out some but the larger 155 main (they ARE Mikunis, right?) should have made up for it at higher rpms.

So how about going back to the original plug. I have bought an Iridium but have not installed it yet, so I can't say for sure, but my understanding is they show improvement with LEANER mixtures.....which might explain why you ran a little better at Mod 5 when going back to a 152.5 main.

Adjust the idle mixture screw again, put in 2 #4 washers and run the 152.5 or 155 on the original plug. Once you have got it running good, put in the Iridium and see what happens.

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sluggo

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Re: Lack of Power at Top End after Mods
Reply #8 - 06/20/05 at 18:27:03

Dingo_Jones wrote on 12/31/69 at 16:00:06:

I was going to post this in a new topic, still might, but here's my recent experience with the sportster muffler.

Last weekend on a trip back to seattle from portland, crusing at a solid 80-85 most of the way, DJ

last weekend ??? what you forget about the mountain ride. Sad

would love to have met you at st helens. maybe next ride.

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Clark

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Re: Lack of Power at Top End after Mods
Reply #9 - 06/20/05 at 19:30:05

It was the spring in the carb. I've had it apart several times and was always careful with the spring, except this time.

I fixed it and have power to spare. Much, much better than before and way better than stock. I was planning to put the #4 washers in this last weekend as well, but the ones I purchased were too big in the OD to fit so I decided to leave it to next week. I'll do that along with the rubber plug/oil leak fix. I know, two things at once, I am doomed.

Thanks fo the help.

Clark

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Reelthing

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Re: Lack of Power at Top End after Mods
Reply #10 - 06/21/05 at 05:13:51

Hey now we know how to make a governer for the bike!

Small bolt with a nut to hold the washer, a drill and the concret driveway will make the diameter conform!

Be sure and get the motor at TDCC before you pull the headcover - that seems to have cause some grief otherwise - and don't twist off the bolts - I find small stuff - a 1/4 inch drive ratchet and a 3 inch long 10mm to help keep the arm energy in check

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Clark Guest	Re: Lack of Power at Top End after Mods Reply #11 - 06/21/05 at 06:09:22 Stupid question What is TDCC and how do I find it? Clark
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Reelthing Serious Thumper Alliance Member Offline Fish or ride that is the question Posts: 5397 Houston,Tx Gender:	Re: Lack of Power at Top End after Mods Reply #12 - 06/21/05 at 11:26:33 top dead center on the compression stroke - if you unscrew large crank cover screw/cap there are little marks you can line up - then take the rocker adjust covers off and make sure there is not pressure on the rocker arms - they'll wiggle a little.
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Savage_Greg Serious Thumper Alliance Member Offline Don't go around your ass to reach your elbow... Posts: 7844 SW Washington State Gender:	Re: Lack of Power at Top End after Mods Reply #13 - 06/23/05 at 19:50:01 This is another good lesson for everyone. Cool.
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Savage_Rob

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Re: Lack of Power at Top End after Mods
Reply #14 - 06/24/05 at 06:29:28

Savage_Rob wrote on 12/31/69 at 16:00:06:

Yeah, there's definitely something amiss. I'm now running a 55 pilot jet and a 152.5 main jet with my MAC installed and she's running pretty sweet right now. I was doing 70-75 in the HOV lane on the way in to work this AM and she definitely had power to spare.

After using several different main jets over a period of months (with either a 52.5 or 55 pilot jet) and paying attention to how each performs, I've decided the best combination for my setup is a 55 pilot and 155 main. The 152.5 main gives just a tad less power to the top end than the 155 and doesn't seem to increase fuel economy at all.

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