New 900 owner.. Few questions

[yz400ex]

I just picked up an 05 900.. Has low compression, but overall, it runs good.. It starts up good, but doesnt really want to idle that well.. Figured I can adjust the idle and fix this, but I also noticed that when the idle gets real low the gauge shuts off and then when you give it gas again it turns back on and the speedo jumps all the way up and back down like it just started again, but it never quit running.. It continues to run with the gauges off, just real low idle.. Is this normal? What RPM should it be idling at? Any help is much appreciated. Thanks

 

[guidoxpress]

what is the compression at?? how did you check it (steps), throttle held open while pulling over motor??

the idling issue is "easy"...the TPS is more then likely out of adjustment..refer to the sticky on the top of the page..it will show you how to make the TPS tester tool, then you can adjust it and your good to go..

once you do the TPS and its still not right...let us know..but it "should" be good after that

might as well replace the TPS harness with the updated one..(you have to cut off about a ft of the old one and splice this one in) $35 p/n# 2203165

 

[yz400ex]

I havent tested the compression, I just know it is low because the motor is fairly easy to turn over (havent tried with the throttle open) and the person I got it from stated it had low compression.. I will test it and will probably re-do the top end depending on the results.. Is it normal for the gauges to turn off at low idle like that and then turn back on when the throttle is applied?

 

[94fordguy]

As far as Idle speed goes, the sled should be idling somewhere in the ballpark of 1500RPM... +/- 200 rpm is ok tho. Seeing as these sleds are fuel injected, the idle is controlled mainly by the computer so I would be willing to bet that the TPS needs to be reset, it is a very common problem, not the only problem, but a common one.

You say the compression is a little low, What kind of compression numbers are you getting?

Does it have good fresh fuel in it?








Oh ya, Welcome to the 900 club

 

[yz400ex]

Thanks for the warm welcome!

I nhavent actually tested the compression yet with a tester, but I will.. I read on here how to do it, but do I do it with both plugs out at the same time and the test hooked to 1 cylinder or do I leave 1 plug in when I am checking the other cylinder? I will reset the TPS and see what happens. The fuel is fresh, but the gauge reads that its low so I will put new fuel in it soon anyway. Thanks for all the help!!

 

[BIGGDAWG]

Thanks for the warm welcome!

I nhavent actually tested the compression yet with a tester, but I will.. I read on here how to do it, but do I do it with both plugs out at the same time and the test hooked to 1 cylinder or do I leave 1 plug in when I am checking the other cylinder? I will reset the TPS and see what happens. The fuel is fresh, but the gauge reads that its low so I will put new fuel in it soon anyway. Thanks for all the help!!

i usually pull both plugs when i do the compression test. you can pull the motor over faster and gives a better compression reading.

 

[94fordguy]

I havent tested the compression, I just know it is low because the motor is fairly easy to turn over (havent tried with the throttle open) and the person I got it from stated it had low compression.. I will test it and will probably re-do the top end depending on the results.. Is it normal for the gauges to turn off at low idle like that and then turn back on when the throttle is applied?

No, that is not normal.

That is a symptom on the low idle, when the sled runs below a certain level the chassis power relay will kick off and start shutting off your gauges, lights, and tail light to try and supply the motor with enough power to keep itself running, when the idle is elevated and the stator is kicking out more power, the relay activates and you have all your bells and whistles going...

As Guido said, either check and reset your TPS if you are inclined to do so, or have it done (depending on your skill and resource level).

I'm not too sure on the compression test, I've never done one personally...

 

[KSH]

How many miles?
Any mods been done?

If no air box mods have been done, when you adjust the TPS , take the boot off the throttle bodies and look through the throttle bodies at the reeds and see if there clean.

Also check the adapter boots for cracks.

KSH

 

[KSH]

I checked my compression with the plug in.

 

[yz400ex]

Ok, here is something else.. when it is running and you feather the throttle a little the speedo moves as well.. not a lot, but does jump around.. what could this be?? As far as mods, it has SLP everything, including airbox and has about 3K or so miles

 

[KSH]

Ok, here is something else.. when it is running and you feather the throttle a little the speedo moves as well.. not a lot, but does jump around.. what could this be?? As far as mods, it has SLP everything, including airbox and has about 3K or so miles

My speedo bounced alot. It's an electronic sensor pickup.

How did the former owner know it had low compression?

You must of gotten a heck of a deal to buy a used sled with low compression with out checking compression and looking in the Y-Pipe.

KSH

 

[guidoxpress]

might be off here..

but on the speedo..it could be switched between the mode settings..where you can change your speedo to a tach and vis versus...is the backround light on the gauges red or blue..

 

[yz400ex]

The lighting is blue..

As far as the deal I got on the sled, I would like to think I did good.. As far as the previous owner, I am not sure how he knew it had low compression. He just told me it did.. Again I havent verified anything.. He was honest and upfront with me about everything.. I am just trying to work out the bugs..

 

[KSH]

might be off here..

but on the speedo..it could be switched between the mode settings..where you can change your speedo to a tach and vis versus...is the backround light on the gauges red or blue..

Your thinkin he's in the tach mode, Sean?

What I'm sayin is that mine would show speed some times when it was idling.

Here is a pic of it.

KSH

 

[yz400ex]

Yea I just went out and checked again and it isnt moving a lot when it is running.. doesnt get past what would be 20 mph, so dont think it is reading it as a tach, but let me know what you think.. Thanks

 

[KSH]

The 900 is a heck of a motor, mine was still running decent when I took it to the dealer for warranty "anti-freeze leak" . Come to find the top end was shot.

KSH

 

[yz400ex]

I am OK with replacing the top end on it, if needed..I should be able to check compression on both sides within the next day or 2.

 

[94fordguy]

I am OK with replacing the top end on it, if needed..I should be able to check compression on both sides within the next day or 2.

Do you know if the top end has ever been redone in it since new? If not, with 3,000 miles on it it would be due to be freshened up anyway...

 

[yz400ex]

Yes, complete motor was rebuilt at 1700 miles and has another 3K on it since.. I figure 3K warrants a top end at the least anyway.. No big deal..


Does anyone have one of these homeade TPS tester tools I could buy from them or borrow or something??

 

[KSH]

Yes, complete motor was rebuilt at 1700 miles and has another 3K on it since.. I figure 3K warrants a top end at the least anyway.. No big deal..


Does anyone have one of these homeade TPS tester tools I could buy from them or borrow or something??

I check if I still have mine. If I do you can have it for shipping.

KSH