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DRZ400 Rebuild no Power!


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I am hoping for a miracle here! I have just rebuilt my 2005 DRZ-400SM (big end and added big bore kit) I have changed nothing else and when I started the bike it started first time and sounds great! Problem, it literally has less power than 100cc scooter, no disrespect intended. I have double and triple checked the cam timing but nothing seems amiss here. It behaves normally till 1/4 turn on the throttle and then the rest of the throttle delivers nothing at all.

I found this thread on Google, seems a guy has had the exact same problem but the thread ends with no solution.

https://thumpertalk.com/forum/archive/index.php/t-457859.html

Any advice would be truly appreciated.

Many thanks

Garry

PS: Apologies if you are reading this for a second time as I only just realised there is a DRZ specific forum..great site!!

Edited by Airtool
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Did you do anything to the head like take the valves out - how are the clearances?

Is the head torqued up to 43ftlb?

Is the carb correctly installed, no big air leaks etc - are the vacuum lines in the head routed correctly/plugged if not used?

Make sure the piston is installed around the right way - engine probably wouldn't fun if not.

Any strange noises at idle?

Its ok to disrepect 100cc scooters 😏

How far did you take the engine down - the big end means you split the cases which opens up a raft of possible issues - ?

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the link gets edited when I paste it in, not sure why. If you Google "DRZ 400 no power" and go to the third link down it takes you there

So you think it might be a compression issue? I will do a test and let you know, thanks for the reply.

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never took the valves out, clearances ok. Big end was done by the shop as this was way beyond me, I just re-assembled and bolted the big bore kit on. Motor sounds beautiful and runs smooth but will only get to about 5000rpm, have taken the carb off and to have a look but couldn't find anything there, all tubes on the carb seem to be in place. Can the electrical 'goodies' on the carb be a possible cause?

Edited by Airtool
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Your running which carb? But no, the throttle postion sensor (TPS) and solenoid restriction (on the CV carb) should not affect things, often people leave it disconnected.

However if your CV carb solenoid air circuit is leaking or open to atmospheric pressure I can see that causing problems....

Sounds like a carb issue or sparking/timing electrical issue to me at this point.... given the engine runs fine up to 5k although -

does your timing look like this?

illust3047.jpg

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Guys firstly many thanks for your interest + advice here, Eddie..I'm honoured. I am going to quadruple check the cam timing (thanks for the pic Svery) but how would I know if the slide is going up, it works on vacuum doesn't it? Going to take a pic of the timing just in case I am overlooking something.

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So there I am test riding my 3/4 dead DRZ with a one end of a pipe on the diaphram-end of the carb and the other in my mouth! Well just by sucking a very small bit the bike bursts into serious life! So it seems there is a problem with the slide in the carb but I am no closer to solving it than that.

Basically the slide does move easily when I suck on the pipe but won't move on it's own, does anyone know why or what could be the cause? I am relieved to be a bit closer to solving this but super frustarted to be so close yet soo far away..I hope at least someone is still with me on this 😏

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The carb came off when the motor was out but other than that it hasn't been touched. It was left in a plastic bin with all the other bits (in retrospect maybe not such a great idea :-/), I am wondering if dirt has got into the part that operates the vacuum. I have checked the hoses and lines and they seem good. I assume it draws vacuum from the intake somehow but not sure if this is internal inside the carb or from an external hose?

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on the flywheel you lined it up either the center of the timing hole or the bump on the centercase (if cover off) with the line beside the T? Chain was tight from crank to exhaust cam? You rotated the flywheel counterclockwise after the cam chain was tensioned and re verified?

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