Engine Rebuild

Skidooslayer687

Skidooslayer687

Member
Joined
Dec 17, 2006
Messages
711
Age
38
Location
Almonte Ontario Canada
Hey guys, been awhile since I've been on the site, lol hay season is in full swing and farmers are breakin stuff left right and center, no time for anything specially tearing the machine apart. Anyways finally found some time to get her apart, I decided last winter that there were close to 10 000 km on the engine so i figured I would replace the rings come summer. I tore into it, got it all apart. I was just wondering what all I am going to have to buy to do this, I know the O rings in the head have to be changed. The gaskets that go from the heads to the coolant rack with the carb heater knob on it are fine because I just left the whole thing attatched to the heads so its one piece. The base gasket is fine, no bends or bangs in it so I wondering if I have to change it as well?? And obviously the piston rings will be changed. Part numbers for the parts would be even better. Also when I tore it apart I noticed dark areas around the wrist pins, the markings are on all of the pistons in the same area, is this blowby? or is this normal? I have pictures but it wont let me post them, says there to large, if anyone knows how to lol please let me know thanks.

Now for the next question, since the motors apart anyways I'm debating on whether or not to get it ported. I am completely new to this I know the basic principles of it and what it does but not sure what the difference between a full lake/race port and aggressive trail porting is. I was just wondering what the difference is and what would be the best to do. I do mostly trail riding but I do drag race occasionally so I'd like some extra power under the hood. Is the engine worth porting i guess would be the question or is it best to just leave it as it is and put her back together with the new parts. Any help is appreciated thanks in advance guys.
 

I'm in the same situation and was thinking about porting.....as states within other post w hp is 155 trail and 165 race (includes case porting) per mrviper.... I believe fuel quality becomes more of an issue with race porting and maybe a narrower power band....but honestly I dont know....most of my time is on the trail as well.....it would be nice to see dyno runs with both set ups to see the difference in air/fuel flow and the torq and hp curve.... I'd also like to now how a trail ported srx and a race ported srx runs against a 1000cc doo.....giving up 300 cc in the 2 stoke snowobile world is huge......I would just like to open the hood and say yupp its a 700 after smoke them doo's
 
sure... fuel is differnt between a trail port job and a race port job as the compression and squish clearances are WAY differnt. 93-94 pump gas will run all day long, no matter how hard you beat it, in a trail port job done correctly because the heads are only lightly cut, the exh port height is only slightly higher then stock, this keeps stock operating rpm, more work is done on the bottoms of the cylinders to promote better air/fuel flow. Where as the race set up the exh and rear booster, rear transfer ports is raised, widened and results in you having to cut the heads more to retain the compression your losing by raising the exh port. the case is also opened up to be able to feed more air to the cylinders which are now enabled to flow more air. I would never encourage someone to try and run a lake race or full race engine to a trail application.
I guess the easiest way to explain the trail port job is your making the engine more efficent, you make it able to get more air/fuel in it with less work, resulting in a nice hp gain. Your doing more widening of ports, then raising. Raising the ports raises the operating rpm, for racing this isnt a problem, but for trail riding its not something I do personally. I like to have guys call first and tell me what they want the sled to do and what mods they have, thier rider weight and thier riding style, I then configure the engine specs to thier needs, as alot of the engines done are not the same specs, they cant be, or they wouldnt work in the application.
I believe this to be very important, this isnt done anywhere else in sleds that I know of, it makes you alot happier with your engine and me happier as I have no customer complaints building them to your needs, not just a general baseline, youll find the baseline companys have alot of complaints as to lost performance, slower then stock, etc.
Best thing to do is research it, then make a educated decision on who and where your going to get work done, ask before you buy!!
 
YOU HAVE A SUPER TUNE ON A GOOD SRX LET ALONE A PORT JOB OR BIG BORE YOU CAN WACK THAT GLORIFIED REV . ESPEICLALLY IF OWNER AIN,T A GOOD TUNER. WHICH YOU FIND ALOT. LIKE ANYTHING ELSE!!! 3:16 (yammie tony)
 
Thank you for the detailed response mrviper, I would definately be going with trail porting then if I decide to. Havn't fully decided if i'm going to leave it the way it is just freshen it up with new parts or do it up, lol the thought of more power leaves a weak feeling in the knees lol. anyways thanks again guys for the help
 
I was still wondering exactly what i should look for and/or replace when its all apart, im positive the bottom end of the motor is in top shape, never had any problems there, however if you guys think I should tear into it then I will. What all should be replaced in the top end of the motor?
 
THE ONLY THING YOU MIGHT WANT TO DO IS INSPECT WRIST PIN BEARING VERY CLOSELY. HAVE SEEN THESE LET GO AND DO A TON OF DAMAGE. OTHER WISE JUST THROW NEW RINGS IN. !! 3:16 (yammie tony)
 
I'd check the piston diameters with 10,000 k's.
I rebuilt mine last year with about the same k's and the pistons were WAY under specs.
I put in three new pistons, rings, cyl gasket, head gaskets, water rail gaskets and one new cyl due to a crack. The only regret I have is that I didn't have the doh for a port job from mr.viper! Now I am looking for an apex rtx and keeping the srx for my back-up.
Still might rip it apart the ol girl again and port it anyways this fall.
If you can afford it then I would say port it!
Just my 2 cents,
mul.
 
mrviper700 said:
sure... fuel is differnt between a trail port job and a race port job as the compression and squish clearances are WAY differnt. 93-94 pump gas will run all day long, no matter how hard you beat it, in a trail port job done correctly because the heads are only lightly cut, the exh port height is only slightly higher then stock, this keeps stock operating rpm, more work is done on the bottoms of the cylinders to promote better air/fuel flow. Where as the race set up the exh and rear booster, rear transfer ports is raised, widened and results in you having to cut the heads more to retain the compression your losing by raising the exh port. the case is also opened up to be able to feed more air to the cylinders which are now enabled to flow more air. I would never encourage someone to try and run a lake race or full race engine to a trail application.
I guess the easiest way to explain the trail port job is your making the engine more efficent, you make it able to get more air/fuel in it with less work, resulting in a nice hp gain. Your doing more widening of ports, then raising. Raising the ports raises the operating rpm, for racing this isnt a problem, but for trail riding its not something I do personally. I like to have guys call first and tell me what they want the sled to do and what mods they have, thier rider weight and thier riding style, I then configure the engine specs to thier needs, as alot of the engines done are not the same specs, they cant be, or they wouldnt work in the application.
I believe this to be very important, this isnt done anywhere else in sleds that I know of, it makes you alot happier with your engine and me happier as I have no customer complaints building them to your needs, not just a general baseline, youll find the baseline companys have alot of complaints as to lost performance, slower then stock, etc.
Best thing to do is research it, then make a educated decision on who and where your going to get work done, ask before you buy!!
Click to expand...

How much power can be gained by trail porting? And how much should it cost? Is a flow bench needed or used when porting sled motors? I'v done a lot of head porting, and sometimes used a flow bench to be sure i was going in the right direction, but i'v never ported a sled engine. Do the same principles apply? And is this something i can do myself?
 
What is the easiest way to remove the pistons from the engine?? If i dont have to go into the bottom end i dont really want to, are the wrist pins pressed in like automotive ones? I'm not used to them at all cuz the big stuff isnt like that, and i've never done a sled engine before, any help would be great guys thanks.
 
If the wrist pins have been in there a while(lot of miles) youll most likely need a wrist pin puller, theres 2 small circlips that need to be removed to get the pin out of the piston. In a pinch you can use a small socket on one side that will just catch the inside of the pin and a larger socket on other side, then place a large c-clamp on them to press the pin out, DONT BEAT out the pin with a hammer , youll ruin the conn. rod bearing below.

justaviper- sure you can do anything your self, but having the correct tools and the specs in which to port the cylinders to is another story. Like for example without a 90 degree porting head($400) you cant do the triple port exh ports on a cylinder. these are the same size as a dentist uses, very samll because the bore is small, so a std 90 degree die grinder wont fit. Its not just a free for all grind away metal, it matters where,how much,what angle, and exact measurements to make them. I will say doing a 2 stroke is alot more precise then doing car heads.
 
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Thanks, sorry for hyjacking the thread. Your hard to get a hold of. I would like to send you my primary, but you havn't responded to the pm i sent you.
 
justaviper, ????hmmmm, I apologize, I am usually pretty good about that, but sometimes its tuff to respond to all of them, during busy times, I get 8,9,10 a day, sometimes I have to just erase all of them because it gets a little over board and the box will only hold 40-50?? resend me a pm, I have it pretty well cleaned out right now. thanx
 
Well i tried removing the wrist pins, got the 2 small circlips out no problem at all, attempted to push the wrist pins out but they would hardly budge, didnt have anything at home to rig a clamp up with so im gonna check at work tomorrow and see if theres anything there, if not i've got a perfect set of c clamps in my box at work that i think will work just perfectly.
 
lol thanks mul, will try that, the clamps i had at work aren't big enough, tried tonight, i'll see if i can find some time this weekend and i'll give it another shot, they've moved a bit i think if they come a bit more they'll just slide out.... lol i hope
 
Well got the wrist pins out this weekend, thanks mul definately worked like a charm. My next questions is about the wrist pin bearings.... how do you know to replace them? they moved freely when the pistons were attatched and there was no binding at all, is there any proper way of checking to see if they need to be replaced?
 
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