Airsick Posted August 15, 2013 Share Posted August 15, 2013 Hey everyone, how's it going? I recently picked up a 79 XS400 and had been riding that around. I finally came back to my DT125 for a camping/motorcycle trip this weekend. I'm starting to loose power when you get to about 4-1/2K to 5K rpms after the bike has been running a little and starts to warm up. I say power loss but it almost acts like it's not quite getting the fuel that it needs. Also along with this is that it has a harder time starting up when it warms up and is experiencing this problem. I'm not sure if this could be a vapor lock issue - not very familiar with that. Any help or advice would be appreciated. Thanks. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted August 15, 2013 Moderator Share Posted August 15, 2013 Next time it is warmed up, take out the air filter and try it again...then report back Link to comment Share on other sites More sharing options...
Airsick Posted August 16, 2013 Author Share Posted August 16, 2013 As an update. I thought that I may be having a fuel issue, my bike has been out in the hot weather for the 6 weeks or so and not I wasn't ridding much since I needed to change my front tire, and I hadn't ridden much. Tire replaced, and then I drained the fuel tank, replaced my inline fuel filter and replaced the fuel line as well with higher quality fuel line. It's running a lot better, I'm still having a slight power issue, but more within the gears itself rather than the engine- if that makes sense. So what happens is that when I'm in gear and start reaching higher rpms 5-6K it acts like it doesn't have a lot of power in the gear, the engine sounds good but you don't really accelerate that much when romping on the throttle, when you shift up to a higher gear, then you can accelerate some more until the same thing happens with the higher rpms. I would say that in 4th gear I was going about 35 or or so. I'm wondering if it's something to do with the clutch or transmission but not sure how to even go about testing. Thanks for reading. Link to comment Share on other sites More sharing options...
nayruf Posted August 16, 2013 Share Posted August 16, 2013 Hi Is the clutch slipping? Have you adjusted the clutch mechanism or the cable? Link to comment Share on other sites More sharing options...
Airsick Posted August 16, 2013 Author Share Posted August 16, 2013 That term sounded familiar but I had to google it. I will be honest I'm just getting into how to actually work on my own bikes. So after learning what the term is, I would have to say yes. I have experienced clutch slipping. I can't say that this has happens all of the time but I have noticed times where the rpms spike and I have no surge in road movement or anything - so long as I understand the term. I have not adjusted the cable. If the clutch mechanism is the bolt that engages and disengages in the crank case when the clutch is pulled then, yes I have started making adjustments to that. I've made adjustments that make it feel like the gears are grabbing and everything, but I don't know exactly what I'm looking for when adjusting it. I put a couple of marks on the bolt to see if it was changing position after I made adjustments. I hope I've been able to describe this well, and thanks nayruf for that comment. Link to comment Share on other sites More sharing options...
Airsick Posted August 28, 2013 Author Share Posted August 28, 2013 Hey I just wanted to give an update about this. So I took my bike out for the weekend 8-17. Well after playing around with my clutch things were working and I was making the best of it. Well after about 40 miles of riding it just takes a dive on me. Turns out I blew the piston and I was mis diagnosing the clutch for bad compression. Well I still think that my clutch will need adjusted but that's where I am. Currently in the Process of getting it replaced. Thanks for the input. Link to comment Share on other sites More sharing options...
blackhat250 Posted August 28, 2013 Share Posted August 28, 2013 You need to up the main jet Airsick " go up 2 sizes , and check plug colour,,, you musta leaned her out on .w.open throttle, or have an airleak,,, Link to comment Share on other sites More sharing options...
Airsick Posted August 30, 2013 Author Share Posted August 30, 2013 You need to up the main jet Airsick " go up 2 sizes , and check plug colour,,, you musta leaned her out on .w.open throttle, or have an airleak,,, Since I'm rather new, How do I adjust the main jet ? And which plugs am I checking and for what color ? Also I'm unfamiliar with the term leaned her out on w open throttle. And what would I check for an airleak? Thanks for your input and sorry for being such a newby that doesn't know much yet. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted August 30, 2013 Moderator Share Posted August 30, 2013 'Lean' means not enough gas in the fuel/air mixture. If an engine runs lean it overheats and if it's very lean it gets so hot...it's burns a hole through the piston crown and you lose all compression. The size of the main jet is stamped into it, for your bike they are in increments of 5, for example only...If you find you main jet is #120 the next sizes bigger are #125 and #130. Air leaks can cause lean running as well as a MJ too small, splits/cracks in the inlet manifold...loose screws...broken gaskets...leaking crank seal (left side) are all possibilities of potential air leaks, it's no use jetting bigger than the makers original spec to compensate for leanness caused by an air leak! Link to comment Share on other sites More sharing options...
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