Savage xl 5.9 revs hanging

[James85]

I thought an air leak would be there constantly. The idle does settle down after a few seconds

[Yoshimoto]

Well its best to rule out general tune before worrying about air leaks-it doesnt sound too far off but deffo lean on LSN.

If it gets to the point where LSN tweaking does not cure this high tickover condition then air leaks/fuel flow are going to be the next thing to look at-the carb is closing-the return spring is in situ,top end seems to be close enough for now its just this low end that seems to be an issue.

 

Sooner or later with all this testing and tuning you are going to start getting a feel for the correct tune-you are not far off as is 

 

i note with interest that on wide open throttle the smoke disappeared after a second or so-perhaps richen-turn out-HSN a little too

 

Yoshi

Edited July 30, 2014 by Yoshimoto

[James85]

Thanks yoshi. Did you watch the carb video? Should the carb slide completely open??

[Yoshimoto]

Yeah near enough but getting it to actually do this with a basic radio can be a chore...worry about this once you are happy that its behaving correctly and running at safe and nippy settings-then you can do some final 'max speed tweeks' to the linkage to get the carb opening how u like if you see fit.

 

In a race situation no mechanic is going to let the carb open less than fully,but for bashing and sport this is going to be down to what you see fit at the end of the day-your truck aint slow-but you are just cutting your teeth with your new nitro tool-one thing at a time will reduce headaches and swearing considerably 

 

Yoshi

[animal47]

Sounds like a lean top end to me. Richen the hsn in 1/8 increments until it starts to splutter and refuse to rev cleanly and then just lean it until it revs cleanly again. Same for lsn, richen until it won't pull away cleanly and then lean it out until you can leave it to idle for a few seconds and still pull away cleanly. My savage was always a bit of a pig as it suffered from a mid tank lean so always had to tune it to be too rich on a full tank.

[sean-vrs]

yea sounds lean and fuel starved at peak rpm's I've had this before with a lean hsn on a 4.6.

Also ensure the glow plug washer is seated correctly, again I've had the exact symptoms there too.

[tomr]

Well its best to rule out general tune before worrying about air leaks-it doesnt sound too far off but deffo lean on LSN.

If it gets to the point where LSN tweaking does not cure this high tickover condition then air leaks/fuel flow are going to be the next thing to look at-the carb is closing-the return spring is in situ,top end seems to be close enough for now its just this low end that seems to be an issue.

 

Sooner or later with all this testing and tuning you are going to start getting a feel for the correct tune-you are not far off as is 

 

i note with interest that on wide open throttle the smoke disappeared after a second or so-perhaps richen-turn out-HSN a little too

 

Yoshi

you have it the wrong way around bud,You should seal your engine first checking for any air leaks etc otherwise you'll be pulling your hair out trying to find a decent and consistant tune.

But hopefully its just lean on the lsn

[James85]

I removed and cleaned the seat of the glow plug. Richened lsn and hsn. Slowly leaned out hsn until it was running well, all gears with good rpm and blue smoke trail (on rich side 1/8th) then slowly leaned out lsn until it had decent punch of the line. Then re adjusted idle gap via screw. A lot better now, however after a high speed run the revs hang until the brake is applied then settle to a good idle. I have a carb return spring already in place.. Could the clutch spring be too tight??

[Yoshimoto]

I cant recommend that a novice removes the engine to try and find leaks before trying to cure the symptom with the engine still in situ,If this cant be cured with tune then i would start to look at air leeks/fuel starvation but not till then in this case-it may well end up going down like this but we have not yet exhausted the simple stuff.

 

Clutch....im not sure you could actually replicate this with a tight/sticky/worn spring.

 

sean-VRS has picked up on a beauty...loose plug...so you had better also look at the cylinder head bolts-a minor leak here will send the mixture way off without even trying and can seriously mess up your efforts..

 

I suppose i had better ask the question now...isnt this engine a 3 needle carb set-up?   If it is then a lean MSN (mid speed needle) could effect the low speed mixture during transition when returning to idle.

 

If it is a 3 needle carb,richening the MSN a 1/4-1/8th turn may open your eyes to the relationship between these 3 critical adjustments and get you 1 step closer to nirvana 

 

Yoshi

[Yoshimoto]

http://www.hpiracing.com/en/part/15250 3 needle carb fo sure 

 

So we are going to slip the mid needle adjustment into the mix too to see if we can make an improvement,this will be a a similar process to the other needles-richen it 1/8-1/4 to start with and see what shes like,bearing in mind that this covers the juice between tick over and 1/2 or 3/4 throttle-this is the rev range we are working on now.

 

Bear in mind how far you turn it from its current position and dont be afraid to over richen it at 1st-this will exaggerate the effects and show you the rev range that you are manipulating.

 

Take your time getting a feel for the exact differences this needle makes-its quite subtle and probably the easiest to ignore.

 

 

 

Yoshi

Edited July 31, 2014 by Yoshimoto

[jimmer7]

Also worth checki g there is not a hole in the rubber carb sleve .

[Anthoop]

I removed and cleaned the seat of the glow plug. Richened lsn and hsn. Slowly leaned out hsn until it was running well, all gears with good rpm and blue smoke trail (on rich side 1/8th) then slowly leaned out lsn until it had decent punch of the line. Then re adjusted idle gap via screw. A lot better now, however after a high speed run the revs hang until the brake is applied then settle to a good idle. I have a carb return spring already in place.. Could the clutch spring be too tight??

If the revs are only hanging now after high revs  and the instant you apply the brake they drop (providing the slide is definitely returning properly)...then yes the clutch could be sticking.

The video from before was definitely lean...the engine had a jittery sound.

 

Simple test- run it round to warm up a bit without any full throttle then bring it back and put it on a block (wheels in the air)......rev to full throttle and let go (watch the throttle slide)- do revs return to idle...then rev to full throttle and brake- do revs return.

If the revs only return when you brake then the clutch is not retracting properly....most times when a clutch sticks the engine will stall when brakes are applied but it is possible that it is just starting to stick and nudging the brake is helping the clutch to retract.

Edited August 1, 2014 by Anthoop

[Yoshimoto]

Listening to the revs and watching the truck i think that its unlikely that the wheel speed is keeping the motor revving high and i would expect a stall or two at the very least.

Servos do not always return to exact center...if the carb slide is open beyond minimum when you let the trigger got to neutral after wide open,this could be the issue.....the carb always shuts fully after a small amount of reverse trigger input but is hanging open if no reverse/brake is applied-this can be cured with trim on the transmitter or adjusting the servo horn on the servo-moving it 1 or 2 splines on the horn to ensure a more positive closing of the slide.

 

On the whole its lean without doubt-when your tuning the needles theres a sweet spot that gives good pick up but still a nice rich mixture,learning the difference between lean and rich even though it seems to be running OK takes experience and a little messing on-but its not too far off as is.

 

After checking slide return performance run it back to back as is and with 1/4 turn or more out on the LSN this will give you a good indication if its LSN effecting tick over-if this makes no odds MSN the same-its the one opposite the lsn on other side of slide assembly.

 

Do not be afraid to richen overall it may loose some punch but this will show you if you are heading in the right direction,the difference between running lean and rich gives several indicators-heat-sound-smoke-running,theres not a lot between the 2 conditions in terms of position of needles but it needs sorting to get good all round performance and longevity.

 

Its been mentioned already-'mid tank lean' you need to consider this when tuning your truck.The settings you make with a full tank may well be less than perfect when the tank is below half full-many of us have this on our savages.Tune when the tank is below half full and then expect a slightly rich behaviour when the tank is fuller-your looking for a good compromise through out the whole tank.

 

 

Yoshi

[Bigjimknickers]

What is lean mid tank then?

[scatteh316]

This is nothing more then a low end that's too rich and a top end that's too lean.

Lean the LSN by 1/8th and richen the HSN by 1/8th and test.

Rinse and repeat until it stops.

[ExLimeyBasher]

Leaky exhaust manifold gasket?

[Anthoop]

On ‎12‎/‎12‎/‎2015‎ ‎21‎:‎47‎:‎19, Bigjimknickers said:

On ‎12‎/‎12‎/‎2015‎ ‎21‎:‎47‎:‎19, Bigjimknickers said:

What is lean mid tank then?

 

Strange to bump a year old thread to ask....but anyway.....the fuel tank is pressurised by the exhaust as you know.....and air is compressible as you know....when the tank is full there is little air and half full and below there is a lot of air....affecting fuel supply. Some models/fuel tanks/engines seem to suffer more than others but in my opinion a lot of it is inexperience.

[Bigjimknickers]

3 hours ago, Anthoop said:

Strange to bump a year old thread to ask....but anyway.....the fuel tank is pressurised by the exhaust as you know.....and air is compressible as you know....when the tank is full there is little air and half full and below there is a lot of air....affecting fuel supply. Some models/fuel tanks/engines seem to suffer more than others but in my opinion a lot of it is inexperience.

Not sure how it's strange to bump, keeping in line with the original post means keeping all the info in one place, which is what a forum is all about?

or do I start a new thread? That's odd to me.

anyway thanks for the answer, I think that may have happened on Sunday when I was tuning it, it kept going lean & I seemed to keep on richening the HSN for what seemed like a full turn out!

[Anthoop]

On ‎14‎/‎12‎/‎2015‎ ‎18‎:‎27‎:‎59, Bigjimknickers said:

Not sure how it's strange to bump, keeping in line with the original post means keeping all the info in one place, which is what a forum is all about?

or do I start a new thread? That's odd to me.

anyway thanks for the answer, I think that may have happened on Sunday when I was tuning it, it kept going lean & I seemed to keep on richening the HSN for what seemed like a full turn out!

Yes in one sense it is good to keep all the information together but you get people replying to the original post (as they have not noticed the date the thread was started).....when that person is not here and the problem either resolved or moved on....it really does not bother me, just explaining.

Be wary that if you are having to richen the mixture and the engine runs inconsistently it could be due to the piston/liner near end of life....could also be an air leak...next time set it rich from the start then get it running and warmed up.... then tune it but keep fuel at least half full......should stay cosistent then.

[Bigjimknickers]

On 16 December 2015 17:37:23, Anthoop said:

Yes in one sense it is good to keep all the information together but you get people replying to the original post (as they have not noticed the date the thread was started).....when that person is not here and the problem either resolved or moved on....it really does not bother me, just explaining.

Be wary that if you are having to richen the mixture and the engine runs inconsistently it could be due to the piston/liner near end of life....could also be an air leak...next time set it rich from the start then get it running and warmed up.... then tune it but keep fuel at least half full......should stay cosistent then.

Yep, exactly that, it was near the end unfortunately, I just stripped it down & it's got no compression at all, I can spin the engine over even with a glow plug in, I figured I'd strip it completely out of interest, but it clearly needs a new piston & liner, these are so expensive on a K5.9 the engine is now scrap.

[sean-vrs]

6 minutes ago, Bigjimknickers said:

Yep, exactly that, it was near the end unfortunately, I just stripped it down & it's got no compression at all, I can spin the engine over even with a glow plug in, I figured I'd strip it completely out of interest, but it clearly needs a new piston & liner, these are so expensive on a K5.9 the engine is now scrap.

Bugger 

[Anthoop]

21 hours ago, Bigjimknickers said:

Yep, exactly that, it was near the end unfortunately, I just stripped it down & it's got no compression at all, I can spin the engine over even with a glow plug in, I figured I'd strip it completely out of interest, but it clearly needs a new piston & liner, these are so expensive on a K5.9 the engine is now scrap.

Boo. ... I had a look on Ebay and you can get bits from the US Ebay reasonably priced but I did not check postage cost.....look up item numbers... 371005071329 and 371128182431 ( those two vitually makes it a new engine for 50-60 quid)....oh and I can not do links.