Jump to content

Loosing power heading into the wind

Recommended Posts

Hey guys new to ThumperTalk and new to the SM world.  I have had my bike for 2 weeks now and love it and wish I had gotten away from cruisers years ago. These are so much fun to ride on the street!.

Anyways. I was heading out onto the highway yesterday and when I was driving into the wind the bike would loose power in all gears and the exhaust would break up and it would cough, sputter and backfire. The bike is a 2009 DRZ400SM with 6200kms. It has a full yoshi exhaust and i know the bike is running a little lean because it does backfire and pop from time to time when i get off the throttle around town and running premium fuel has helped a little bit. I have the jet kit coming to deal with the lean condition and so i can do the airbox mod.

I was just wondering if anyone has come across this issue in the wind? It only happened when i was driving directly in the wind. If the wind was behind me I had no power issue getting up to highway speed and keeping it there. At first I thought i had just accelerate too hard and drained my fuel bowl, but I did several loops alternating with going into the wind and with the wind. It always broke up and lost power into the wind and had not issue going with the wind. I also noticed when heading into the wind it would gain or loose power depending on the throttle position. ie when rolling into the throttle partial throttle was shitty then i would hit half throttle and it would take off then at 3/4" it would loose power again. My thought is air fuel mixture and at certain throttle ranges it pumps more fuel through and the air/fuel mixture gets closer to where it needs to be hence the power turning on again. 


Thanks in advance!

 

Share this post


Link to post
Share on other sites

If you're going to rejet for the 3x3, there may be no reason to diagnose this now. Do the rejet and see if this still occurs.

  • Like 1

Share this post


Link to post
Share on other sites

FYI, the Drz400SM has a PAIR valve system that causes that popping noise-i removed mine and the popping noise was all but eliminated-this component is not needed on these bikes and once removed does not influence rideability or fuel consumption at all.

Share this post


Link to post
Share on other sites

Thanks for the information! I am just getting ready to rejet which means this is the right time to rip all this shit off so i can get it dialed in correctly!

Share this post


Link to post
Share on other sites

it happened to me with cross wind, but i already had a jet kit and i had some home made thing to keep my knee from been cold whike riding to work last winter. im not sure what fixed it but i removed my home made stuff (it was mist likely changing the airflow on/around the bike, creating some "turbulances") and i also raised the needle up.

Share this post


Link to post
Share on other sites

His won't have the pair valve up in Canada I don't believe . As for the wind , some models of bike do have issues with cross winds and certain headwinds from the wind going over/around the panels and it causes a low pressure zone where the airbox is trying to suck in air . It looses the ability to get enough air and sometime ends up with the slide fluttering(DR650's do this), all bad for keeping power . I've noticed mine does it sometimes with a strong wind coming from the right IIRC , seems to be a little "off" .

 

.

Share this post


Link to post
Share on other sites

Interesting. That is kinda a piss poor design. Especially for a bike that's set up to be run on the street. Mine being an SM. 

i was looking yesterday briefly for the pair valve and was wondering if I actually had one. It's possible that it doesn't because we don't have emission requirements. Old it still have the solenoid though? That was the one piece I thought would be obvious to see and couldn't see, to find it with my brief look. 

Share this post


Link to post
Share on other sites

Listen to Ohio, the carb vent hose can be a problem. Run a vent hose up into the still air under the fuel tank and see if it gets better.

Share this post


Link to post
Share on other sites

sounds good folks! I will try the vent hose relocation. It is pretty short so i will have to get a longer one. I will do it when i do the jetting.

 

Thanks for all the help. Still pretty new to these kinda bikes. My old 84 Maxim 650 never had problems like this and was way easier to work on. haha

  • Like 1

Share this post


Link to post
Share on other sites

So update time:

Relocating the vent hose seems to have worked. My bike does not have the pair valve system.

I installed the jet kit last night and discovered that someone had indeed been in the carb and also that the 3x3 mod had been done on it.

The float bowl bolts had been replaced. It was running a 155 main jet. and 22.5 pilot jet with the factory air screw. The needle didn't have blue or red on it and the clip was set all the way to the bottom groove. I assume it was the factory needle and someone just changed out the main jet and perhaps adjusted the clip setting.

I installed the blue needle with the clip set on the 3rd (how it came) and went to a 160 main jet and changed to the 25 pilot jet and am running the Keihin adjustment screw with it set at 2.5 turns out.  

I have a full yoshi exhaust and the 3x3 mod.

The popping and farting on downshifting has pretty much cleared right up and the pulsing feeling I used to feel on the bottom end while lightly accelerating is gone as well. I read somewhere online that this happens when you are running lean.

The bike feels way faster and it is now a wheelie machine in first gear without really even yanking on the bars.

 

Tonight i plan to pull the spark arrestor and do a final dial in of the air screw.

Do these gauges have the ability to read out the RPM?

 

 

  • Like 2

Share this post


Link to post
Share on other sites

Stock computers don't have a tachometer, but you can grab one off ebay for cheap if you want. My bike runs exactly at 5k rpm at 50mph with 15/44 gearing on 18/21 inch wheels, shouldn't be too far off on an SM.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×