Question about 1987 Yamaha SDR

1 Answer

Losing power when it gets hot

After riding for a short while my 1991 bravo begins to lose power and the idle gets rough

Posted by on

1 Answer

  • Level 2:

    An expert who has achieved level 2 by getting 100 points

    MVP:

    An expert that gotĀ 5 achievements.

    Novelist:

    An expert who has written 50 answers of more than 400 characters.

    Governor:

    An expert whose answer gotĀ voted for 20 times.

  • Expert
  • 126 Answers

Are you turning off the choke after its warmed up? bike will not run right if the choke is left on and will seem like its losing power. if its off, then read on.

pull the spark plug and take a look at it. does it look like light brown toast (as it should) at the end that goes into the cylinder or does it look like it is brand new (still white)? if it looks brand new, then its indicating a lean condition and will run very hot (you may see evidence [blueing] on the exhaust pipe where it exits the cylinder head) and stop running. hopefully damage was not done to the piston (usually a lean condition will put a hole in the top of the piston). if its a lean condition, then read on.

so what's causing the lean condition? have you recently added a high flow air cleaner or after market exhaust pipes without rejetting the carb? or maybe you had to rebuild the carb, bought a kit from a dealer and the size of the jets were not correct? if you can return things to the "before" condition one at a time, then you can determine what change caused the problem.

good luck.

Posted on Jan 18, 2009

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

'87 Yamaha ProV 50: Will cold start and idle well. After a full throttle 1-2 min run will begin & continue running very rough near idle. Will die without addtl throttle imput.


Hi Roderick:
I'm not familiar with your engine configuration, but on some of the older bikes, vibration eventually can cause a wire to break in the coil. When the engine is cold, the wires make contact and it runs, but as soon as it gets hot, the connection is broken or compromised and the spark quits or drives you crazy.
Since your bike runs when cold and quits when hot, I'd be looking for electrical rather than fuel problems.
Hope this helps.

Sep 09, 2015 | Yamaha Motorcycles

1 Answer

50cc running rough when warm


dirty air filter acts like a restrictor which is like leaving choke on. as is ok cold could be this or could be ht lead or ht cap breaking down when hot cos of bad connection

Feb 13, 2013 | Motorcycles

1 Answer

2001 flstfi runs rough at idle and on highway


Hi Robert, and the usual suspects are:
1. Spark plugs in bad condition or partially fouled.
2. Spark plug cables in bad condition or leaking.
3. Spark plug gap to close or to wide.
4. Faulty ignition coil, module and or sensor.
5. Battery nearly discharged.
6. Damaged wire or loose connections at battery terminals,
ignition coil, or plug between ignition sensor and module.
7. Intermittent short circuit due to damaged wire insulation.
8. Water or dirt in fuel system, carburetor or filter.
9. Fuel tank vent system plugged or carburetor vent line closed off.
10. Carburetor controls misadjusted.
11. Damaged carburetor.
12. Loose or dirty ignition module connector at crankcase.
13. Faulty MAP, CKP, and or CMP sensors.
14. Incorrect valve timing.
15. Weak or broken valve springs.
16. Damage intake or exhaust vale.
For a prime suspect please visit website below and good luck:
Big Twin Carb EFI DTC Intructions codes Harley Davidson Forums Harley...

Oct 21, 2012 | 2001 Harley Davidson FLSTF - FLSTFI Fat...

1 Answer

Flhtci 2000, 103screamin eagle upgrade,fron of motor jumps at low idle,more than i think it should,bolt broke?rubber mount wore out?


It could be a problem with your rubber front engine mount or it could be that the engine is no longer balanced like it used to be. Check the front engine mount for cracks or any faulty condition.

Now, from the factory, the engine is roughly balanced so as not to shake too much. To do this, be weigh the pistons, rings, wrist pins. Then the factory drill large shallow holes in the flywheels to "balance" the assembly. Now,when you install the upgrade, you changed the piston size drastically and if this included a "stroker" crank, the crank may not be balanced as closely as the original. Also, the camshaft was probably changed. A more aggressive profile camshaft will cause the engine to idle just a bit more rough as well.

Stock engines are designed to idle smoothly. High performance modifications usually do result in the lose of this smoothness.

Ride Safe.
Steve

Jan 16, 2011 | 2000 Harley Davidson FLHTCUI Electra Glide...

1 Answer

My ninja loses power in the wind


Do you have a "RAM AIR" system on that bike, if so that may be what happens when you ride into a headwind. The bike may be running a little lean and with the extra intake pressure goes too lean.

Jun 06, 2009 | 1999 kawasaki ZX-6R Ninja

1 Answer

Interupted power


try installing new plugs, sounds like you you may have a fouled plug.  is the bike hard starting?

Jan 04, 2009 | 1998 Honda XR 600 R

Not finding what you are looking for?
1987 Yamaha SDR Logo

Related Topics:

245 people viewed this question

Ask a Question

Usually answered in minutes!

Top Yamaha Experts

Steve Sweetleaf
Steve Sweetleaf

Level 3 Expert

1128 Answers

D. E. Hev

Level 3 Expert

1059 Answers

mikeuk

Level 2 Expert

61 Answers

Are you a Yamaha Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...