New top end or re ring 98 mountain srx 700

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Gerryjackman

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I am looking at doing a new top end or just re ringing my 98 mountain srx. Right now hot psi is at 105 on all 3 very close sled does run amazing just looking to get it back where it should be. Does anyone know if I should change the pistons too? It's got around 8500 km on it I'm not sure if I just re ring it and it would be fine or change the pistons as well. Also do I have to do anything with the cylinders get them honed or anything I really have no idea just heard guys say it. Appreciate the help guys thanks
 

If you are taking it apart do rings for sure. You can check the pistons and see if they are still in spec. If so you can reuse them, or just replace for a piece of mind. You can also check the cylinders for spec as well.

When I redid my SX700 (pistons and rings). I did get the cylinders honed as well. If memory serves me right the cylinders are nikasil plated and take a special hone.
 
How do you know if you should hone the cylinders out or not also would best bet best to go with stock yamaha rings ? Does anyone have a proper break in procedure after I get the girl back together?
 
I just honed them anyways. Basically it just puts little new cross hatches I believe in the cylinders to help the rings seat.

Yamaha OEM parts all the way.

First tank of fuel mix 50:1. Don't hold the throttle wide open and avoid going to max rpms. Basically just take it easy about the first 100 miles. Let the sled warm up well before you ride it. I like to feel the heat exchangers just warm to the touch.

Others will say just ride.
 
You say first tank 50 to 1 is that actually mixing it in the tank as well as what the oil pump already injects ? Also I've heard to not use full synthetic oil is this true ?
 
Just another quick question my compression is right around 100 give or take. Few where should it be at? And would I notice any power gain at all by re ringing this ol girl?
 
Gerryjackman said:
Just another quick question my compression is right around 100 give or take. Few where should it be at? And would I notice any power gain at all by re ringing this ol girl?
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im in wisconsin so its a different elevation but mine has 138 psi on all 3, take them out, get new rings, measure pistons/cyls to spec and hone, at 8500km it probably could use some preventative matienence, for the first tank of gas or so i would run 50:1 plus the oil injection to help seat the rings, just dont beat on it and youll be fine
 
Anyone know of piston specs I will take cylinders in to get honed but pistons I'm not sure whether to look at new ones or not. Do you think I will get more power out of it if I can get it up to 130 or around there ? Or will I even notice
 
One more question do you guys know if full synthetic oil is ok for break in I've heard guys say not to use synthetic for break in can anyone shed some light ? Thanks
 
just take a green scrub pad and wash the cylinders good in hot soapy water.Cross hatch should still be fine,pretty hard stuff.After my rebuild my compression is around 124-125..I am sure if you run a higher compression..you better use #1 fuel only..
my cross hatch was still fine after around 6000 miles.you just want to clean any varnish in the cylinders.
 
Wouldnt see why you couldnt use synthetic for break in. But Ive always heard once you go that route you cant go back. Just my opinion but I dont think you need to add oil to gas. Im with the opinion of others on hear that you are actually leaning it out. Any yami I have ever owned seems to be plenty fat on oil calibrations. I know I used to work at a Yami dealer and set up alot of vipers at the time and we never put oil in gas for break in. Yamaha to my knowledge never recommended it. If they did we would have been doing it. Now cat did recomend it when I set up those sleds. So again different opinions. Think you would be fine by not. But as one poster said use some common sense. Dont go out there and pin it to the bar up a mountain. Use varying throttle positions as you ride and take it easy for couple days. Then drive it like you stole it.
 
So I tore it down tonight everything looks fine actually pretty good carbon deposit are covering all the piston basically a little Rich I think but I did run it in the mountains without re jetting and had issues. I called the local yami dealer guy gives good info he said to definitely bring the cylinders in to get honed I know they always usually say that so I don't know what to do there. There is not much wash below rings but I'm still hoping doing the rings will bring my compression back to 125 130 or so. I'm still fairly new to wrenching on the inside of engines and I'm wondering how the cylinder keeps compression in when the port to exhaust is open? May be a dumb ? But I can't figure it out. The pistons had quite a bit of play side to side but were all the same it's about a 1/4" maybe a bit more is this okay?

Once everything was torn down I had a peek around and just my luck all three v force reeds had chipped at least one of the petals. I'm assuming I shouldn't run it like this so that leads me to my next ? What are good reeds fair priced and will hold up a while? And could bad reeds be the reason I have lower compression I don't think so myself but need to know from someone who does !!!

Appreciate the help guys if I ever get pics figured out I will upload some
 
Any help on the reeds I'm going I try and get some today ? And the synthetic oil during break in do u guys of anyone who would know a for sure answer on this
 
Ur piston play is normal should be some. But inspect closley and make sure your crank bearings are moving freely. No binding or squeaking and such. My understanding that if you pay 15 scoots you are a vip member and therefore you could download a service manual from this site. Thats a smokin deal since most cost 30 bucks. That way you can look up this stuff and have your own piece of mind and make sure stuff is within spec. Sounds like you got lucky with the reeds. Just chips probably just got blew through. Have heard of broken pedals causing major internal damage. From what I have read on here the stock reeds are just as good as V force so I would go with whatever you can get first. Far as that oil thing look at it this way . Most all the new sleds run some form of synthetic oil right out of the box. You will be fine with it. Here again some swear by it others not so much. Get bored do a search on oil on this site sometime. Will provide hours of reading enjoyment.
 
Reeds might have been causing the low compression numbers. Also every compression tester reads differently. I have one that reads consistently 30 psi low. I use that one whenever Im buying something new. Unless your sled has had the odometer rolled back, an srx motor is just warming up at 8500 km. My viper motor has 18000, never been apart and still runs strong. My buddys srx hit 21000 last night, never been apart. And another buddy has 23000 on his stock srx motor. But now that you have it apart might as well rering it at least. I would disassemble completely and reseal and inspect the bottom end.
 
Ok my compression numbers Are all very close and the damage on the reeds isn't consistent this leads me to believe it is still the rings I should change I'm trying to figure out why I only have 100 psi hot compression tho with such little KMS also why my reeds are chewed up like they are any help?
 
Hey should I be washing off the carbon build up on my pistons or does that matter it seems to be a little rich it does have light spots not very big tho where u can see the piston top but majority is black w carbon build up does this matter or is washing it off a good idea or not ?
 
alot of differnt opinions here, none of which I do.

1.) hone cylinders with a 240-280 grit stone

2.) place new yamaha rings on the pistons with the "T" facing up on them

a.)coat them in 2 stroke oil(cheap stuff) and spin them a couple times once on the piston, this way the oil is in the groove of the piston.


b.)line up ring gaps with the pins in back of piston

c.)wipe a finger smear of oil in the cylinders and install over the pistons, the bottom of cylinder is tapered so it compresses rings, just be sure to keep ring gaps aligned to pins on piston back

d.)reinstall rest of engine componets, fill up with coolant. Start sled up and check for leaks make sure everything is good, let it warm up till the exchangers on the floorboards are warm to the touch,vary the throttle and double check it all. If good,... your done put away all your tools and go relax for awhile.

let sled completely cool off to room temp, warm it up 1 more time and ride it like you want to ride it. Once you heat cycle the rings like this they are broke in, NO extra oil needed to be added to gas, not revving it up for the first tank, none of that is needed. Cheap oil is the best for break in but just for the rings, if you already have synthetic oil in the oiltank it will be just fine.
take it out and ride it as normal, it will be just fine........ :sled2:

for the reeds, youll get alot better life and no differance in power by reinstalling the stock yamaha ones, they are very good and work great in everything but a all out race engine.
 
Right on man appreciate the input! I have another ? I have v force reeds in the sled right now havnet pulled them yet I don't know what model it is either if I order stock yamaha reeds will they work in there will the boots be the same I'm not sure if u have to change those when putting in v force or not I would like to order today so they be here by weekend would it be safe to say that they will work with what I have right now?
 
Gerryjackman said:
Right on man appreciate the input! I have another ? I have v force reeds in the sled right now havnet pulled them yet I don't know what model it is either if I order stock yamaha reeds will they work in there will the boots be the same I'm not sure if u have to change those when putting in v force or not I would like to order today so they be here by weekend would it be safe to say that they will work with what I have right now?
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no, the yamaha reeds wont fit the vforce blocks, you need to just put 3 stock yamaha srx-600/700 or viper reed blocks in.
The carb boots are still stock you dont have to change those out when you put in vforce reeds. You can still get replacement petals for vforce but youll need to call them. I would just put 3 stock yamaha reed blocks back in alot less problems and no power loss.
 
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