Out for this season..sigh...

alrite... sounds good... looks like ill be splitting the cases to change the seals as well then... anything I should know before hand... going to be literally my first engine I take apart myself completely... lol
 
How did you clean the carb jets? It really should be done with the proper sized drill bits with your fingers. Blowing air or spraying carb cleaner through them will not do the job.
 
I used a small coper wire and ran it through the jets... and then sprayed carb cleaner where the copper wire didnt go in the carb.. and made sure when spraying the carb cleaner that there was a steady flow not a mist...

thats why im steering away from a carb problem as I cleaned them very well... and made sure there where no restrictions... now there's ofcourse always a small chance that a piece or dirt blocked something... I will be checking them out soon and will see... but yea... before I rode it.. I thoroughly cleaned them...
 
Ride.Race.Live said:
Yea... ill have to try that out when the engine is up and going... Hard to tell... right now... with the way the plugs are... i know modsrx and concept are not far from me if i do need some help with something if they are willing.... but yea...

What are some seals that I should check out? anything in the engine that could cause a air leak? and have this happen
Click to expand...


let me know if you hit a road block, crank seals are easy to change and are dirt cheap. You will need a puller for the mag rotor(the cheap powerbuilt one that is reversibile for inside or outside worked for me, or you can push the rotor off with bolts. I prefer the puller less stuff to do), also get yourself some yamabond.
 
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ahh ok... bonus I think we got one!...

Remember seeing something like that in the garage somewhere... might be wrong... but well see...

thanks!

Hopefully I find the root cause... cause as of now.. Ill just change where I get gas... though everyone else on sleds get gas the same place i go...
 
great good to hear stagss thanks!

question for you guys right here...

Would you guys recomend moding my 01 to have dcs on it? if its possible... im starting to thing it would be a good idea for me... I know alot of people think it can be a headache but seems to me... if you got your sled going good... then its a good thing to have!

if so... can ya point me in the right direction... on what I would need.. what can just "hook right up"and what would need some cutting?
 
Its not that SPI are not any good its just that stock Yamaha pistons are as good as it gets!

IMO:

I would only use an after market piston if you were unable to get stock ones

I do know an engine builder thats doing a lot of BB Cats[F7s-F8s], he uses SPIs and has very good luck with them in that application.
 
if you change the seals & leave those main jets in the carbs it will melt another piston. a good trail ported 700 srx w/ stock air box should be 155's w/ stock compression considering the lousy quality of today's fuel. 157.5 w/ gutted air box.
bob
 
Yea I will definatly be re jetting the carbs no 2 questions about that!

I was talking to bendersrx and the jetting where set up for up to -15C degrees... I rode it around 1 weekend when it was -20 didnt put much km's on it but still rode it... Dont know how much bigger I will go yet will need to do some testing.. as the jetting was recomended by mrviper and all that... but i will increase them... and go from there...


I was asking more or less about spi/spx as the oem pistons are going to be out of my budget...

But when I read up about them.. it seems like a hit or miss... some people have no trouble... and some say they will never use them again...

guess ill compare the prices and go from there... I already more or less got a spi piston on the way with a black hood and light for a clutch kit i bought...
 
My thoughts

Ride,race,live as you asked, I looked at your pics.
What I see from the pics is the correct wash marks on the domes, the pto cylinder with the biggest jet(150) looks the worst, too rich is why theres no carbon build up and still the front edge of piston eroded...,I will explain why shortly..

The center not so great...same 148.8,but it looks too rich as lack of carbon, and its all shiny not dry as being lean, it also shows the wash marks as needed.possible p/v problem/adjustment on this cylinder?.

The mag looks the best with a even amount of carbon on dome and wash marks at the rear,and side trans ports,this also runs the smaller 148.8 main jet so the part its "too lean" doesnt apply as suggested.

The second part of my observation looking at the exh edge of the pistons is eroded away,and the fact that they have carbon built up on the erosion and not silver from fresh detonation tells me it was done a while ago,not just since you were out when it was -20 below. Most likely from before you bought the sled, this can happen slowly if the detonation is only slight and happens a few times. This was likely from a tank or 2 of low octane fuel, it happens even to stock sleds.

You have a couple options to play it safe, the jetting specs I give for these are good to -10 degrees ,this is with premium fuel which is 93 octane,plenty rich and makes very good power. However, If you ride when its colder out or the quality of the gas where you use the most is not trusted,then you either can bump up the jetting SLIGHTLY, AND, add more octane. Adding more octane makes the sled richer with no carb adjustments!! I tell every single person in these days to always use octane booster, even on bone stock 2 stroke sleds!! Look at the amount of burndowns that have been on this site in the last 2 years even with bone stock sleds, so the suggestion the porting/wrong carb specs ruined it is not true.
If the carbs are set up to specs and spec fuel is used they are just as reliable as stock,its the fuel companys selling us short on quality and or lack of octane. A bottle of booster in the trunk is much,much cheaper then pistons. Sure,it wont make 87octane fuel into 93, but it will take the edge off premium if its a little short,and certainly not a big task to add. Use 1/2 bottle to a full tank, so you get 2 full tank fill ups to 1 bottle of booster. Again,its cheap insurance even on bone stock sleds, much cheaper then pistons!

Cold weather jetting:
42.5-45pilots (depending on how aggressive clutching is)
1.75 turns out on fuelscrews
needles 4th groove with both shims on top
152.5mains across, (more then likely you can use 150's all the way across because your richeng up the midrange circuit which overlaps with your mains.but if you have questionbale fuel or very cold a whisker richer main wont kill it off too bad power wise.)

airbox can have a couple extra holes in top but needs to retain the center baffle cone.

yes, this is same jetting I use for a std 780, it will be more then rich enough in your 700 and with octane booster as insurance youll be plenty rich, more jetting then this and it will be hollow sounding,flat and too rich resulting in noticeable loss of performance.
 
you have a trail engine running on inconsistant quality pump fuel. you want to pull the cord & go have fun & beat up on your buddies & not be concerned w/ engine failure.
srx factory jetting - mains:
2000 - 147.5,146.3,146.3 - too lean ( engine failures ) so yamaha changed it for 2001
2001 - 150,148.8,148.8 - good all around
2002 - yamaha went back to 2000 spec. because they now had DCS ( that's why the DCS flashes )...detonation sound waves.
a good trail port job ( if that's what you have?? ) should raise h.p. to around 155. that's 11% more h.p.. a simple linear equation: w/ a mikuni slide rule change round jet to hex jet number. multiply the hex jet # by 1.10 = the new main jet size. convert back to round jet size. since safe stock jetting is 150,148.8,148.8 that means safe all around jetting for various conditions would be 157.5 for a "good" trail port job. this covers you on the coldest nite w/ the crappiest fuel...but you won't need a tow home.
bob
 
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