Stock 2010 DRZ400SM Cant Go Faster than 105KMPH?!

[jmpl]

Hi all,

Heres hoping someone here has ideas on why my DRZ400SM cant get past 105 KMPH without intense vibrations...

So its a stock 2010 DRZ400SM, its great for pretty much everything I do (daily errands, sunday rides and weekend camping trips away)
But recently, Ive noticed the bike simply cant get past 105KMPH without intense vibrations coming from the engine.

The shuddering starts at around 103KMPH in 5th gear with the throttle open at whatever RPM that is typically , hard to check as 2010 DRZ400SM has no RPM counter.

Changes Ive made on bike.

-Sprockets are 15/39 with a 110 chain (stock is 15/41 with a 110) I did this to ease the RPMs on the motorway and in theory I should be getting higher top speeds than stock, not lower...
-Reshimmed the valves a couple months back, these were on the very edge of spec so a shimmed to the middle of the range for future proofing.
-Standard ACCT in it, but have checked and reset this, both timing chain and ACCT are working as they should.

Im under the impression the stock DRZ400SM had a decent top speed of at least 130kmph, so whats going on here?? I weigh a mere 65kgs!

Anything else I should be checking?

Cheers all

[FJRider]

Hi all,

Heres hoping someone here has ideas on why my DRZ400SM cant get past 105 KMPH...

So its a stock 2010 DRZ400SM, its great for pretty much everything I do (daily errands, sunday rides and weekend camping trips away)
But recently, Ive noticed the bike simply cant get past 105KMPH without intense vibrations coming from the engine.

The shuddering starts at around 103KMPH in 5th gear with the throttle open at whatever RPM that is typically , hard to check as 2010 DRZ400SM has no RPM counter.

Changes Ive made on bike.

-Sprockets are 15/39 with a 110 chain (stock is 15/41 with a 110) I did this to ease the RPMs on the motorway and in theory I should be getting higher top speeds than stock, not lower...
-Reshimmed the valves a couple months back, these were on the very edge of spec so a shimmed to the middle of the range for future proofing.
-Standard ACCT in it, but have checked and reset this, both timing chain and ACCT are working as they should.

Im under the impression the stock DRZ400SM had a decent top speed of at least 130kmph, so whats going on here?? I weigh a mere 65kgs!

Anything else I should be checking?

Cheers all

A Dirty or Faulty Fuel Intake System Can Cause Engine Shuddering. A poorly set up or dirty fuel intake system can easily cause the engine to shudder and shake.

Check your engine mounts for broken or damaged rubber engine mounts ... or loose bolts first.

Smaller sprockets (in theory) will reduce RPM at the various speeds you travel at ... but it takes longer to GET to those SAME speeds ... as your horsepower is not increased. You are actually effectively REDUCING the horsepower at the back wheel. To get more horsepower ... you need to get a better supply of fuel into the cylinders (see above about poor fuel supply issues). Gravity feed fuel systems seldom achieve that well ... especially on the smaller motorcycles.

Your motorcycle was fitted with gearing for it's optimum performance. Gearing it up will do more HARM than good to the engine.

Short of a turbo or a decent fuel pump ... and/or a higher octane fuel ... your plan will flop. And this will probably kill the engine too ... sooner than you may think.


Put the OLD sprocket back on ... and see if the problem persists.


Let us know how you get on.

[jmpl]

A Dirty or Faulty Fuel Intake System Can Cause Engine Shuddering. A poorly set up or dirty fuel intake system can easily cause the engine to shudder and shake.

Check your engine mounts for broken or damaged rubber engine mounts ... or loose bolts first.

Smaller sprockets (in theory) will reduce RPM at the various speeds you travel at ... but it takes longer to GET to those SAME speeds ... as your horsepower is not increased. You are actually effectively REDUCING the horsepower at the back wheel. To get more horsepower ... you need to get a better supply of fuel into the cylinders (see above about poor fuel supply issues). Gravity feed fuel systems seldom achieve that well ... especially on the smaller motorcycles.

Your motorcycle was fitted with gearing for it's optimum performance. Gearing it up will do more HARM than good to the engine.

Short of a turbo or a decent fuel pump ... and/or a higher octane fuel ... your plan will flop. And this will probably kill the engine too ... sooner than you may think.


Put the OLD sprocket back on ... and see if the problem persists.


Let us know how you get on.


Cheers for the quick reply!

-The bike definitely only begins to get this juddering at 104 ish KMPH so I think I can rule out fuel intake as that would be apparent at low RPMs as well right?
-Will check engine mounts / bolts before next ride.
-Interesting what you say about the sprockets and horsepower. Done this on simple motorcycles like the DRZ in the past and had no issues. Only reason for going to a 39T on the back was to ease the RPMS at higher speeds on motorways etc even if it takes a bit longer to wind up :) Pretty sure its not the sprocket change cause the issue, but will certainly chuck it back on to test for any difference!

Any other suggestions for what I could check on the bike specifically?

Thanks again

[FJRider]

Cheers for the quick reply!

-The bike definitely only begins to get this juddering at 104 ish KMPH so I think I can rule out fuel intake as that would be apparent at low RPMs as well right?
-Will check engine mounts / bolts before next ride.
-Interesting what you say about the sprockets and horsepower. Done this on simple motorcycles like the DRZ in the past and had no issues. Only reason for going to a 39T on the back was to ease the RPMS at higher speeds on motorways etc even if it takes a bit longer to wind up :) Pretty sure its not the sprocket change cause the issue, but will certainly chuck it back on to test for any difference!

Any other suggestions for what I could check on the bike specifically?

Thanks again

Worn Out Spark Plugs ... when were they last checked/changed ??

Blocked air filter may cause it ... often ignored.

Fuel blockage/poor supply (as previously mentioned) ...this may include ..

1. Kink in the fuel line.

2. Blocked inline fuel filter.

3. Blocked fuel filter on the petcock (the one IN the tank)'

4. Blocked jets (partially or otherwise).

5. Fuel floats not "Floating or stuck. It's hinge pin not seated correctly.

[jim.cox]

dirty airfilter would be my guess