y srx hard to start and not vipers

[jefsnow]

seems to me....

Good point...where the problem with the fuel feed would be is after the fuel tank has been drained, the sled has been run out of fuel,or any time the fuel line has become void of fuel. In these cases, you would need enough suction from the pump to restart the "syphoning effect" or you would need the fuel level above the top of the fuel feed line loop to refill/restart the flow from the tank to the pump. Something that would not be uncommon in the fall or after a long sit.

your tests done without reed valves in place, or power valves removed, eliminates the suction from the engine, doesn't it ??

 

[sideshowBob]

your tests done without reed valves in place, or power valves removed, eliminates the suction from the engine, doesn't it ??

Reeds were in place but power valves were not.
You definately would need the reeds! The power valves might have a slight effect[they don't seal airtight], but I think the fact that the pipes + power valves were not on and the reeds were DRY[as in new] definately would have some effect. It still had 2 - 4 psi pulse and would not pump my SRX pumps but had no trouble pumping the SX pump[may be due to a more flexible diaphram???] As I stated, when it fired up it pumped no problem...it was only at "Recoil" speeds.

All good thoughts + interesting info.

 

[sideshowBob]

...........***UPDATE 3***.........

This is the latest info on my SRXs re starting...previous info follows below.

-stock fuel loop in place
-SX 700 fuel pump
-3/4 tank of fuel
-TPS stock setting
-sled sat outside overnight[20 hrs]
-7C/20F
-full choke/no throttle

3 pulls and idles fine

--------------------------------------------------------------------------

[/Quote] ***** PREVIOUS INFO******

Today I drained all the fuel from my sled again[2002 SRX]:
- checked the fuel filter - OK

Reinstalled stock fuel loop:
-had to add @7 imperial gallons[@28 litres/@9 us gallons] in my sled before fuel would gravity flow from fuel loop.

Installed 1999 SX 700 fuel pump[no vent hole in bottom, fittings all the same, + looks identical externally to SRX pump except it does not have rubber X-over line]:
-pulled sled over with recoil - instant fuel flow from all fuel lines!
-reinstalled New SRX fuel pump...still no fuel when pulled over!

Conclusion:
-either I am getting dud SRX fuel pumps or they require a fairly strong pulse to operate
-I have installed the 99 SX700 fuel pump and will be using it[it operated fine on our SX when it had a Bender 800 BB kit with TMX 38s]
-reinstalled stock fuel loop and when the sled has sat for a long period I will make sure I have more then 7 gallons in the tank so fuel can gravity feed!

Additional Info:

I hooked up a primer bulb from a boat tank to one of my hand held SRX fuel pumps to see how fuel would flow thru the pump:

-when bulb was squeezed fuel came out the oil line fitting only.
-if I held my thumb over the oil line fitting and squeezed the bulb, fairly hard, fuel would VERY reluctantly flow from the fuel line fittings

Hope this info helps...do with it what you may!! LOL!

Things that make you go HMMMMM ! Keeps it interesting![/QUOTE]

 

[bluemonster1]

got to be an answer to this.Tried starting my SRX since it was sitting in the garage for 2 weeks,80 pulls later I was winded.Put fuel in plug holes and fired right off.Went to my SXR600 that was sitting for a week since last start and on first pull it fired,second pull it was running.What gives here.Maybe I should get a pump off a SX to replace SRX pump.I wander if the pumps are actually different.I will look up a parts fiche to see if the part #'s are the same or not.
What a STRANGE situation.

 

[northern srx]

Would there be a spec. showing fuel flow rates for the different pumps(SRX/SX)? Curious to see as SSB had no issues feeding a BB SX motor with stock pump!?!

 

[sideshowBob]

Would there be a spec. showing fuel flow rates for the different pumps(SRX/SX)? Curious to see as SSB had no issues feeding a BB SX motor with stock pump!?!

I would like to see flow rates as well. I have the old SRX pump apart and the rubber hose has a bypass type pressure valve from the lower level of the pump to the mid level. It flows one way only, lower to mid. The rubber line appears to be a fuel return line from the lower diaphram output feed back to the upper level supply side of the pump.???
I am cautiously using the SX pump as Yamaha changed their three cylinder pumps for the SRX + ultimately the Viper for a reason, and I would not be using it had I not had experience with the SXBB.[none of the aftermarket SX Big Bore companies, that I saw, ever gave directions requiring a change in fuel pumps.]
My experience is that the SX pump, that I have, does pump way more fuel "on the recoil" then either of my SRX pumps, under the same conditions, I don't know if that is "typical".

JM.02c

 

[bluemonster1]

they are different looking pumps for sure..
SXR part # >>8CH 24410-00-00
SRX part # >>8DF 24410-10-00

 

[snomofo]

they are different looking pumps for sure..
SXR part # >>8CH 24410-00-00
SRX part # >>8DF 24410-10-00

Well it finally came down to lighting my sled for the first time this year and after reading through this thread I had planned to test a bit. I'm always aware of open fuel in my barn with the open flame of my wood burner so I usually keep it to a minimum.

I have an air box on the front door covering the fresh air vents (similar to high effeciancy home furnaces) that goes into a four inch vent to the outside which has really helped keep negative pressure inside the barn low and reduce drafts and also minimize low floating fumes from igniting.

But I still am uncomfortable with open fuel (unless I drag it outside) so I did not monitor fuel delivery to the carbs. I did however try some new things since last time and wanted to share with the group.

Starting with a bone dry tank, I added 4 gallons of fresh fuel (still well below the fuel line loop) and then rocked the primary back and forth using a surpentine belt, cracked the float height/drain screw on the PTO carb, nothing.

I then pulled the plugs (which is what I'd normally do) and cranked it normally three tugs. Cracked the screw on the PTO bowl and I had fuel.
Put the plugs in dry (no premix), and within two tugs 2 of the three were lit and within 10 seconds at idle the third (MAG) finally lit.

As background, I can tug 10-15 (plugs installed) with the same amount of fuel in the tank and it will not start until I add premix down the cylinders.

It appears that without the plugs installed I can pull it over fast enough to activate the pump and fill the bowls. To confirm this conclusion I could measure the pulse to the pump with and without the plugs installed but the variability of tugging could account for any differences in pulse strength.

I have an 0-120 "H20 gauge I could tee into the pulse line. I think it'd have enough resolution to see any differences.

Frankly, I am bit tired of working on the thing so it looks like I'll be pulling the plugs, tug it three or four times, install the plugs and lite 'er up in the future.

Bottom line: Pulling it over faster with the plugs removed is enough (for me anyhow) to overcome the fuel line loop and or SRX low delivery during cranking pump.

I would guess as long as all of the passages/chambers/diaphrams/springs are the same, max flow shouldn't change from the SRX to SX pump. I know in automotive applications we over flow-rate pumps at least twice max consumption.

 

[9801srx]

Y SRX HARD TO START AND NOT VIPER. been trying to figure this out for a long time and finnally i know why. the reason is that there is a slight difference in the viper carbs choke circuit than the srx,two things actually. they are the choke jet in the float bowl {brass tube that hangs down next to the piolet screw} is .044" orfice size on a srx ,viper is .056" which makes it easyer to draw fuel up out of the float bowl and the second difference is the choke air bleed this is located under the black cap on top the carb just ahead of the throttle slide. on a srx the hole is just drilled aprox 5mm on a viper the 5mm hole has a brass insert pressed in which reduces the bleed size to approx 3mm ,this restricts the bleed air and allows more engine vacume to draw the fuel out of the float bowl which make the choke circuit much richer on a viper at pulling speed. to test i made the approprate mods to my wifes 98 srx 700 carbs and now instead of 30-50 pulls in -25c it starts in 5-7 pulls after sitting a week . hopfully this puts the srx starting problems to rest for good.

 

[jaydaniels]

Y SRX HARD TO START AND NOT VIPER. been trying to figure this out for a long time and finnally i know why. the reason is that there is a slight difference in the viper carbs choke circuit than the srx,two things actually. they are the choke jet in the float bowl {brass tube that hangs down next to the piolet screw} is .044" orfice size on a srx ,viper is .056" which makes it easyer to draw fuel up out of the float bowl and the second difference is the choke air bleed this is located under the black cap on top the carb just ahead of the throttle slide. on a srx the hole is just drilled aprox 5mm on a viper the 5mm hole has a brass insert pressed in which reduces the bleed size to approx 3mm ,this restricts the bleed air and allows more engine vacume to draw the fuel out of the float bowl which make the choke circuit much richer on a viper at pulling speed. to test i made the approprate mods to my wifes 98 srx 700 carbs and now instead of 30-50 pulls in -25c it starts in 5-7 pulls after sitting a week . hopfully this puts the srx starting problems to rest for good.

Well, that makes perfect sense. I was thinking about the fuel pump issue a bit more and there should be plenty of gas in the float bowls to start the sled regarless of how well the pump is 'pumping'. Like you have said in this post, it seems that the design of the SRX carbs makes it difficult to pull fuel out of the float bowls at cranking speeds. I would actually be interested in some more info and a few pictures on this mod as I'm getting sick of pullin' my guts out. Great info, thanks.

 

[Ride.Race.Live]

well.. you can do the mod.... or you can think of it in another way... alittle bit of exercise and stratching of the arms before the ride lol...

Im guessing the viper carbs are different and dont fit on the srx which would solve it?

 

[9801srx]

well.. you can do the mod.... or you can think of it in another way... alittle bit of exercise and stratching of the arms before the ride lol...

Im guessing the viper carbs are different and dont fit on the srx which would solve it?

no ,the choke circuit is the only difference i can find other than jetting. the easyest way to do it is to use a set of viper carbs, but you have to use all the removable brass from the srx carbs [ piolet ,main ,needle jet,jet needle and piolet air jet ] and possibly the throttle slide[ not sure if that is different between the two.

 

[sideshowBob]

Y SRX HARD TO START AND NOT VIPER. been trying to figure this out for a long time and finnally i know why. the reason is that there is a slight difference in the viper carbs choke circuit than the srx,two things actually. they are the choke jet in the float bowl {brass tube that hangs down next to the piolet screw} is .044" orfice size on a srx ,viper is .056" which makes it easyer to draw fuel up out of the float bowl and the second difference is the choke air bleed this is located under the black cap on top the carb just ahead of the throttle slide. on a srx the hole is just drilled aprox 5mm on a viper the 5mm hole has a brass insert pressed in which reduces the bleed size to approx 3mm ,this restricts the bleed air and allows more engine vacume to draw the fuel out of the float bowl which make the choke circuit much richer on a viper at pulling speed. to test i made the approprate mods to my wifes 98 srx 700 carbs and now instead of 30-50 pulls in -25c it starts in 5-7 pulls after sitting a week . hopfully this puts the srx starting problems to rest for good.

Nice work!

Who would have thought Yamaha would vary the choke circuit from one tripple's 33mm carbs to another!

 

[9801srx]

Nice work!

Who would have thought Yamaha would vary the choke circuit from one tripple's 33mm carbs to another!

ya i know, i notice you have a sx 700 . next time you have the carbs off could you check if they also have the brass insert in the choke air bleed hole also and the size of the choke fuel jet. i used torch tip cleaner to find the hole size. just for cureocity.

 

[Ride.Race.Live]

A somewhat simple fix for something that was a fairly large mistery! though it was very small specific things that caused it...

now lets see how many viper carbs are going to sell in the for sale forum!...

awesome work figuring it out!

though im still abit confused as some srx's still only took a few pulls to start... the most I pulled mine so far in about -15 -20 celcuis was 6-10 times.. exept for that one time I forgot to pull the kill switch and pulled god knows how many times (was around -25 outside n just though it was like my 00 to start when cold)...

 

[snomofo]

A somewhat simple fix for something that was a fairly large mistery! though it was very small specific things that caused it...

now lets see how many viper carbs are going to sell in the for sale forum!...

awesome work figuring it out!

though im still abit confused as some srx's still only took a few pulls to start... the most I pulled mine so far in about -15 -20 celcuis was 6-10 times.. exept for that one time I forgot to pull the kill switch and pulled god knows how many times (was around -25 outside n just though it was like my 00 to start when cold)...

From what I can gather, three different starting issues have been talked about on this thread.

Super cold hard start
1,2 or 3 week soak hard start
Pre-season hard start

I could see the differences in chokes between Viper and SRX affecting the first and second and the seeming differences between SX and SRX pumps affecting the third.

My issue has been with carb priming during preseason prep. I found by pulling the plugs and tugging three times at the increased crank speed I can fill the bowls. Once they're filled, I've gone nearly a month without starting and two maybe three tugs and it's lit. Never an issue with low temps either.

I'm a lefty pushing #230 and an SRX owner without issues one and two. Nice find regarding the differences between choke circuits and maybe it could explain some other's issues but I'm happy to have sorted and eased my preseason start up... and discussing with fellow TYers.

 

[unchained]

I HAVE HAD THREE. 1999 , 2000, 2002. 99 WAS EASY, 2000 IS A JOKE ITS SO EASY, 2002 KILLS ME EVERY TIME I GO TO START IT. UNLESS ITS BEEN RUN. I AGREE '' NATURE OF THESE BEASTS ''. 3:16 (yammie tony)

My 02 takes 10 pulls in the morning. Otherwise runs excellent. My 99 always started on the 3rd pull.

 

[sideshowBob]

So far the most pulls my 2002 has taken this year is 8 after sitting overnight at -4F/-20C.[I shut it down with the choke for overnights] When its warm it has been starting on the first pull everytime, used to take 2-3 pulls warm in the past.

 

[Feeze]

Interesting thread but this is my story...... I have a 98 srx600, 98 MVenture cross and a 98 MSRX. The srx's have been excellent starters 5 pull max on the coldest days. The MVenture is harder to pull mostly because of the recoil design vs. the srx recoil.

At the end of the season last year the MSRX went down....detenation from bad gas from a small town...

Normally at the end of the season I pull the carbs off & plug all holes, but for some reason I decided to prepared the other 2 sleds for summer storage by doing the typical gas stabalizer. Now I have this same problem WITH THE srx600 & MVenture!

When I pulled the carbs at the start of the season I noticed alot of gumming residue in the float bowls, so I cleaned them the best I could (so I think)Interesting enough, I do not have a problem with the MSRX.

So, after reading through this post I have come to the conclusion that I need to due what Ding said and find the problem. I don't think it has anything thing to due with different jets, pumps, fuel line routing, etc. I think it is a "dirty component" from bad fuel! It is either in the float jets, fuel filter or fuel pump.

I will let you know what I find!

 

[SRX it is]

Cleaning the fuel pump

I have a 98 with a Hauck 800 kit w/ 35+MM bored carbs, so it isn't exactly the same. With that said mine took forever to start as well. I decided to take everything apart and clean it, fuel pump included. The carbs had already been cleaned but did it again anyway. The things that made the difference is in the fuel pump.
I took it apart and separated very carefully all three sections. It was pretty clean, there were two parts that I took note of. First, in the center section of the pump there is a check valve the machined hole that the black diaphragm between the center and the base sets on. With the large hole is a tiny bypass hole that I guess would allow fuel to fill the center section. This hole was blocked, I sprayed it with carb clean and blew it out with compressed air. I figure once fuel is in the center the pulse from the crankcase is more effective as it doesn't compress like air does. The second thing I took note of is a check valve under the brass fitting that has the crossover line. I unscrewed the fitting, removed the spring and the valve was stuck, I used a pick and popped it loose. I cleaned and reassembled. The carbs, lines and the pump were dry. I have the stock line locations, up and over the airbox. I pulled it over 22 times with a 1/4 tank of gas and it fired. That may seem excessive, but it was dry with low fuel. The next test at 28F cold, 3 pulls. Now it starts first pull after sitting for 15 to 20 minutes. Thanks to all on this post for the information that led me to try this. My pilots are 50s this may help, mains 1/2 157.5, 3 160