Savage xl 5.9 revs hanging

[James85]

Hi, I bought a used savage xl recently and after tuning it ran great. However it has now developed a fault and I can't seen to shake it.

It revs up fine through all gears, good smoke entire rev range but when I let off the throttle I hear the revs sticking high instead of dropping back to idle. This happens for maybe 3-5 seconds after WOT then returns to normal idle.

I've tried messing around with all meddle settings but nothing seems to work. Any ideas guys? Thanks

[atom3624]

When the 'revs hang' can you see the throttle closing properly? Is the action smooth?

Al.

[James85]

hi, it only does it after a high speed run so by the time I get near it's back to normal. I can't replicate it on the bench. Throttle seems smooth enough when operated on bench

[James85]

hi, it only does it after a high speed run so by the time I get near it's back to normal. I can't replicate it on the bench. Throttle seems smooth enough when operated on bench

[Yoshimoto]

The symptom your describing could be a slightly lean low needle-a trapped/blocked fuel line/debris in your carb needles or a poorly set carb/linkage or as simple as the tank lid is not shut tight-When you are sure that the carb slide is returning to tick over position when you let the stick or trigger return to center try enriching the low speed needle an 1/8th-1/4 turn and see how this affects it.

You could try the pinch test to get a better idea of the low end mixture too 

 

Yoshi

Edited July 21, 2014 by Yoshimoto

[James85]

Thanks. I tried richening up the Lsn but it didn't seem to do much. I tried the pinch test. The revs raised just before it cut out after 3-4 seconds of the pinch.

[Yoshimoto]

Hmmm....if you have any extra fuel/exhaust filters/coolers fitted make sure these are well sealed and not dragging air anywhere.

if its a 3 needle carb mid needle may also effect the revs not settling if its slightly too lean.

With the air filter off make sure that the slide closes properly with some minor spring tension holding it in the fully closed/tick over position-when they get warm and moving these can hang up if theres not enough 'push' from the linkage.

Make sure your tx and rx cell are tip top too as voltage can sometimes effect servo center positions.

Failing any of the above being to blame make sure the carb is well seated in the crank case and also consider re-sealing the engine.

Does it run at sensible temperatures overall? do you have a temp gun to use? the spit test may also be of help to you in determining overall running temp/tune to try and pin the issue down.

 

Yoshi

Edited July 21, 2014 by Yoshimoto

[James85]

Thanks yoshi, I will double check the linkage. I have no additional filters. Thinking about linkage actually.... I have an issue with the brake rod, it doesn't actuate the brakes untill it is pulled round to almost 9 o clock position. The rod also is not secure. I've ordered replacement rod and cam. I wonder if this imbalance with the throttle/brake servo could be causing my fault

[Yoshimoto]

Yeah a poorly set servo arm/linkage could allow some play in the carb rod at extreme angles-unlikely to be the brake itself but could be a good clue to point you in the right direction 

A couple of times ive had this happen with various engines-an engine and carb/carb stack re-seal cured it instantly when all other reasons were ruled out.

Temperatures would be a good indicator at this point.

 

Yoshi

[James85]

I think I will fit the brake rod when it arrives then reset the carb to factory and start tuning from the start. I was worried it my be an air leak

[Yoshimoto]

Depending on use/age its easy to assume that a seal and check over of the engines mating surfaces including the needle stack wont do it any harm if you are so inclined 

If any engine is difficult to start...doesnt tick over endlessly....behaves less that perfect in any way the final bug bears to eliminate are the head bolts,needle stack,carb neck,backplate-assuming that i can eliminate all other causes.

 

Yoshi

[Anthoop]

I've tried messing around with all meddle settings but nothing seems to work. 

Never mess around with needle settings...maybe it is just how you wrote it (?)...try to set up a regime of how you set the carb.....

HSN- wide open throttle runs.

LSN- acceleration tests.

Idle gap- prevent clutch engaging at idle.

 

Always in that order and always start from rich/wide makes things easier....and always stay on the rich side of best performance.

 

Other than that...listen to Yoshi.

[James85]

Thanks anthop, the thing is... It runs fine, hits all gears with a slight trail of blue smoke at wot. Acceleration is spot on too, wheelies no problem. After a few seconds the idle drops down to normal. That's why I started to try adjusting the carb because I couldn't decide where the fails lies.

[jizwizard]

if its slow to idle that points to a rich low end. Lean it out and then adjust idle to suit

[animal47]

I would be inclined to richen the hsn as it sounds too lean at the top end hence the revs hanging, after a few seconds the lsn is obviously rich enough to calm it down.

[James85]

Update. I reset to factory and tuned. Revs still hang and also once warm it revs at idle now!! I have 1mm throttle gap. Where should I start??

[Yoshimoto]

Its lean.liquid fuel is restricted/slowed or air is too abundant...IE leaking in some where or both.

 

Yoshi

[James85]

Richen the lsn ??

[Anthoop]

Video of high speed and acceleration possible?

 

Only tune the engine when warm, if you tune when cold it will be too lean when warm.

The throttle gap does not have to be at 1mm, it is a good start point but invariably it will need adjusting in conjunction with the LSN.

[Yoshimoto]

Very good point Anthoop

 

Try this...

 

1st-Start it and as it warms up adjust the gap to keep it ticking over well but not too high to make the clutch engage.This may take several tweaks as it warms up fully.

 

2nd-The tickover should now be sensible,and the engine is up to running temp.Do the high speed needle on full speed runs until your happy with your setting-clean high speed revs on full speed-dont worry if its a bit raggy/smokey up to the halfway or so throttle point thats next.

 

3rd-LSN last.Your looking for a steady tickover and seamless transition through the low to mid/high rev range-during this adjustment you may well again have to alter the gap on the slide to get a sensible tickover-either up or down.

 

If at any of the 3 stages you cant achieve what your looking for then theres an issue elsewhere.

 

Take each stage one at a time in order,if any one is not right it will effect the result of the next stage.

 

 

Yoshi

Edited July 30, 2014 by Yoshimoto

[James85]

Here is a video. You can hear the revs hanging. Also near the end when I blip the throttle the revs stay high and actually engage the clutch and the truck moved off itself

https://m.youtube.com/watch?feature=youtu.be&v=pHzseC9OgRs

[James85]

I also lost front wheel drive tonight. The prob is getting drive so it must be the diff

[James85]

Here is a short video of the carb slide operating. I checked this when the fault was happening with the engine running. The slide always went back to closed position

https://m.youtube.com/watch?v=R1cfEKgSf6Q&feature=youtu.be

[tomr]

That sounds like an airleak possibly the front bearing best to whip the engine out and check it.

 

[Yoshimoto]

It does sound lean-and is behaving as if it is.

LSN out A/C 1/8th turn and see if this settles her down-if not another 1/8th until it calms down but still gives sprightly pick up-dont worry too much about leaks until the basic tune can be seen to be not working.

What i would do is LSN out a 1/4 turn to start and see what this behaves like-often the factory 'holy grail' settings are just a starting point-lots and lots of engines tune up well with far from factory settings but the factory settings will get you going.

 

Yoshi