2000 srx is slow

M

Moodeyblue

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Aug 18, 2014
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47
Location
sherwood park
I have a 2000 srx that is giving me top end issues. has trouble reaching 100 mph

what is done to this machine:
new pistons and rings
trail ported
stock pipes
heads machined
compression 110 on all 3
new stator
new TPS
boysen reeds
carbs taper bored
crankcase ported
152.5 MJ
45 PJ
raised needles 1/2
1 1/4 ripsaw stretched to 128
stock drivers
23/38 gearing
heel clicker clutching. can only get 5 grams on tip max. for 8400 to 8500
red spring
silver secondary
45/37 helix


this machine sometimes will hit 8500 but lays down at 95 mph. I used to have a 1 3/4 track and I thought this was the issue. changed to 1 1/4 this year and not much better. this is on a well packed surface.

Not sure if this is a timing issue? the machine actually runs strong, plugs are good but lays down on top.
could reeds be an issue? these are not old but this machine has never run as strong as my 3 previous stock srxs (1998, 2000, 2001).

any help is welcome.
 

Did u check your plug color ....its gonna be hard to hepl since u did alots of stuff ...
 
1. check power valves
2. harness rub
3. clean carbs
4. mouse nest
5. belt deflection to spec
6. get new rings
7. not in love with h/c for top speed
8. replace both spring primary and secondary
9. clean clutches
10. new plugs and gap.
start here 3:16x (yammie tony)
 
op says he just put new pistons and rings in it. until it breaks in fully, 110 psi is not too bad for a fresh motor
 
you certainly don't need a silvr sec. spring with that helix, a green at 60 should yield some more topend as the silver will be too stiff and try to backshift the sec clutch fighting the front clutch, makes it feel flat at topend.

edit add: also, how do you have the weight set up in clutch weights, 5 grams in the tip is light for a srx, it might be you have weight in the middle hole???
 
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5 grams in tip. none in middle. my old stockers used to run 6.5 in tip.
silver at 3/3, always ran this with my srx's. maybe not optimal for top speed but my old sleds always ran better. I have a green spring I can try.
this machine actually launches really well. just lacks on top.

would it hurt to play with the tps?
 
after reading that current clutch set up, it would seem its not making power then if its that light gram wise, as the clutch is actually a good generic dyno.
Do you have a stock carb rack you could try??
 
you posted new pistons and rings. but than 110 psi. and i assume this is heat cycled and run. i would take this again with a different tester and cold. i would of thought you be alittle higher. 3:16x (yammie tony)
 
No spare carb rack.
this machine must have 300 miles after he top end. I has been giving me the same issues for 3 years now. Pulls really strong on bottom but lacks top.

last weekend I did 3 speed runs on the lake 1/2 mile??? installed 8bu weights (55 gms) with hauck orange and my 45/47 and silver spring.
the first time it ran 8500 and approached 100 mph. 2nd time it had trouble with 8300. 3rd time was worse.


This is a new stator on the sled a couple of years ago.
power valves are clean and I proven the servo is working. the cables are not pulled through.

When I increased the length of the track to 128", I removed the rear heat exchanger and installed a temp gauge. this sled typically runs 140 F. I don't think this is too hot but could it pull timing?

I bought this sled at haydays 4 years ago and fully overhauled, powder coated, new bearings and engine mods. The crank is in phase and it was trued up when I removed it for the crankcase porting and new crank seals.

at a loss.
I will check my tps settings tomorrow.
 
on my 3 previous SRX I would get around 120 with my tester. this is at 2200 ft. I often see others getting higher results than what I am getting. I will borrow a tester and check again.
this srx has always been lower than my previous machines. it was trail ported and heads cut, but this is where it is at now.
 
When your heads were cut was the squish correct after? My stock 02 is 130+ on 2 different testers at 1300ft.
 
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find a friend with a srx that will let you try it(stock carb rack), I have seen more then once a bored carb rack cause problems, it has to do with boring them, if the idle well is opened up when boring them it will pull fuel from there and ruin the flow. The carbs need to be offset bored to be done correctly, and when someone taper bores they usually don't offset it, and sometimes they leak from sides of slides.
While your compression reading is on the lower side its not going to make it laydown like that, you notice compression gain or loss at more low/midrange running, more compression stronger it is. What is the squish clearance in it?

when you make your first pass.. have you ever stopped the engine with kill switch,coasted to a stop,remove plugs and observed the piston tops and plug readings? is it rich or lean?


edit add: carbs from 2000-02 srx will interchange
 
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mrviper700 said:
find a friend with a srx that will let you try it(stock carb rack), I have seen more then once a bored carb rack cause problems, it has to do with boring them, if the idle well is opened up when boring them it will pull fuel from there and ruin the flow. The carbs need to be offset bored to be done correctly, and when someone taper bores they usually don't offset it, and sometimes they leak from sides of slides.
While your compression reading is on the lower side its not going to make it laydown like that, you notice compression gain or loss at more low/midrange running, more compression stronger it is. What is the squish clearance in it?

when you make your first pass.. have you ever stopped the engine with kill switch,coasted to a stop,remove plugs and observed the piston tops and plug readings? is it rich or lean?


edit add: carbs from 2000-02 srx will interchange
Click to expand...

today I cc'd the combustion chamber with the number #1 piston at tdc. I was able to get 24 cc up to the top of the spark plug hole. I believe the sparkplug accounts for 2.25 cc so combustion chamber volume is at 21.75.

is this the correct volume for porting...or is the problem with my low compression?

I checked the tps today and it measured 2.3 Kw. this was replaced 2 years ago and was on spec then, but now it has changed. ordered a new one today also. hopefully this is some of the cause.
 
the size doesn't sound bad of the chamber but what is the squish clearance?? as its likely wide. Remove the pto sparkplug, take a small piece of lead solder and bend in a "L" so it will reach the side of the bore, inser this into the bore thru sparkplug hole while holing onto the long stem. Bring the cylinder to TDC via rotating the primary clutch, keep the solder going across the engine from right to left so its inline with the wristpin, otherwise the piston can rock forward and back and skew your reading. compress the solder and then measure the thickness.

I would not be convinced that's why it lays down up top even if its a large clearance.

I would first try a set of stock carbs on it and see what rpm it will pull with zero clutch changes, I'm guessing it will likely go up and pull more rpm meaning its making more power.....
 
mrviper700 said:
find a friend with a srx that will let you try it(stock carb rack), I have seen more then once a bored carb rack cause problems, it has to do with boring them, if the idle well is opened up when boring them it will pull fuel from there and ruin the flow. The carbs need to be offset bored to be done correctly, and when someone taper bores they usually don't offset it, and sometimes they leak from sides of slides.
While your compression reading is on the lower side its not going to make it laydown like that, you notice compression gain or loss at more low/midrange running, more compression stronger it is. What is the squish clearance in it?

when you make your first pass.. have you ever stopped the engine with kill switch,coasted to a stop,remove plugs and observed the piston tops and plug readings? is it rich or lean?


edit add: carbs from 2000-02 srx will interchange
Click to expand...

OK last week, I changed the heads to some smaller cc heads I used a few years ago. the compression is now up to 115 psi. volume of heads with piston tdc is 20.75 cc. measured squish at .049".

while the heads were off I noticed a power valve with a cable pulled out of it. I am happy a found this but it surprized me as I assembled this engine a couple of years ago,and it was always a pooch. Must have happened at the time.

When testing 2 days ago, I immediately installed another gram in the tips and it was over revving at 8600. I typically try to run at 8400. the machine easily pulled up to 100mph.

yesterday I took the machine to the local snow drags and placed 2nd in both the 7 imp and 9 imp. While I prefer to win, it was up against some strong machines and I am happy with the results. the sled was hitting just above 90mph (speedo) at the end of 660ft.

Mr Viper- I will look for a spare set of carbs and try this as well. hopefully it is even better.
when the carbs were tapered bored, I don't believe he went up to the idle well, but I will confirm when I remove the carbs next time.

Thanks everyone for your support.
 
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