My spree build

[bbrmotosports]

Well this build has had my pulling my hair out. I have the BBK, MLM pipe, 21mm carb kit and gears and slutch springs. I could never get it to run quite right and have any low end power. Well I pulled the engine out and in the mean time I bought an 86 spree for parts. I figured I would start from scratch and built a high compression engine. After I tore my 84 down I noticed the crank was shot, had plenty of up and down movement on the rod and I also was running 2 base gaskets which changes the port timing on top of me already porting it 1 width. Long story short I assembled the engine and gave it to my machinist to do the head work so I don't need to run 2 base gaskets. He cc'd out the head and made the head fit the BBK bore. he also took some material off the head surface of the cylinder and also rechambered the head for the now domes piston to keep the fire under the plug like it should be unlike how it was stock it was burning on the edge of the piston. I went from 95 PSI of compression to 235. The E start does not work when the engine is cold but once it's warm the E start will crank it over. I just got it in the scoot an hour ago and took it for a ride. Holy balls is this thing fast now! has plenty of low end power and once it hits the power band it burrys the speedo in no time flat. If the rain lets up i'll see what it does on GPS for speed but i'm super impressed with this setup. On this build I had no issue with running race fuel so thats why we built so much compression with it. I run VP110 in it. Here's the head, it's also now a 4cc combustion chamber

[paulpauly7]

i think 235 psi is a bit over the top .Are you sure your guage is accurate.If so lets run it and see how long it runs

[ClemSpree]

+1, that's a whole bunch, watch the detonation.

[bbrmotosports]

Yes, I only own snap on tools. I'm running race fuel so it doesn't detonate

[swimmingfree]

not saying your tool is not wright but its hard to bleve its that your compression test is wright... 235 it is the highest i have seen on here.. if i was you i wood barrow a tester from autozone and see what it reads ...
swimmingfree

[LMH]

235 and you wont be kicking it easily or the e start to work. Take a pic of that compression test. The real issue here is that your engine builder more than likely did not account for stretch of the connecting rod under high rpms, with that kind of CR I imagine the squish band is less than .005 which is riding the head. Id like to see 235 psi on a spree engine.

[LMH]

Im mostly interested because I have an extra spree engine, and realistic cost for machine work is nil.

[bbrmotosports]

Squish is .050. I'll do another test to satisfy you guys
And I'm not even going to secong guess my builder. He builds thousands of engines for snowmobile race teams.

[swimmingfree]

if your testing with the same gauge it may read the same....
swimmingfree

[bbrmotosports]

Well it better lol. I'll use my cheapo gauge in a lil bit here.

[swimmingfree]

you dont have to by just barrow it.... your compression so hi i think you have a deasle motor ... how hot dose it run???? the higher the compression the more heat you will have....
swimmingfree

[bbrmotosports]

Its pretty cold out here now. Its in the 50s but last night I had 180-210.

[swimmingfree]

180-210 is on the cool side.... are you sure your reading the gage wright ???? or are you using the metric side??
swimmingfree

[bbrmotosports]

Yes, I'm reading a digital inferred temp gauge correctly. I only rode it for 10 min yesterday. I'm going to go ride a tank if gas out of it today

[bbrmotosports]

Yes, I'm reading a digital inferred temp gauge correctly. I only rode it for 10 min yesterday. I'm going to go ride a tank if gas out of it today