Engine Work Junior Jackson 4 strokes Snowbikes

[wwillf01]

I keep reading about this engine builder and his work on hill climb, snowbike, arena bikes... anyone here have 1st hand knowledge or has used him for an engine build?

I am steering away from big bores and going with a straight engine set up....porting, cams, piston, dynotune.....

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[M5-]

Its easy to get power, its hard to get power that's durable. I've been running the GYTR CNC ported head on my YZ with the factory race cams. It rips pretty darn good, I run the stock piston so I'm not married to race gas but they do offer the high comp version. For the price, which BTW is a lot you, can't hardly beat the set up. Actually you can buy new CNC heads for the 14-17 YZ now for pretty cheap on Ebay. By the time you pay an engine builder, by parts etc etc it adds up pretty quick. With the GYTR part which is a work of art its a bolt on, the cams come with the valves already shimmed by Yamaha. Bolt it on, add a tune and go.

Just an option to consider. FWIW I agree on the skip the big bores thinking.


M5

 

[hillclimber147]

The modern day 450mx four strokes are already putting out pretty good HP/cc. Push them any further and you are reducing the maintenance intervals drastically. And I'm not talking about just oil changes here, stuff like adjusting valves, replacing valves/seats, cams, cam chains, pistons, cranks,...... etc. Stuff i'd rather not worry about when i'm in the backcountry. I hillclimb in Billings, MT and have heard of my fair share of 70+hp 450 motors blowing up. And this is just with a few practice rides in btw the few competition runs these motors go thru. I'd love that kind of power but not over the reduced reliability.

 

[Wheel House Motorsports]

There is definately a fine line of pushing things crazy hard and just helping it work that little bit extra for our application.

I personally ran a 14 yz 450 with stage 2 hotcams, a 13.5:1 piston and a HOT ignition map for over 200 hours on snow, sold the bike and it had 300+ and was still ripping when the next guy sold it. And it was not treated nicely, i ran it into the rev limiter for fun on a regular basis. All on 91. It had a distinct extra pull on the top end vs a stock moto bike and was honestly pretty miserable to ride in the dirt it was so snappy. Being stock bore and everything it reved super fast and just screamed into the higher RPM which helped maintain trackspeed and never bog the engine down.


I see the OP is in UT. you can easily run higher comp on premium. This helps give back some of what elevation looses. Depending on the bike not sure who/what is available to make it work better. but since we are asking the bikes to do nothing but make top end HP, setting up a motor build for that can make a much stronger running bike.

 

[wwillf01]

That was my thought because it's running in a very specific environment only at high altitude during a cold winter I should be able to get a little more out of the engine if not good bit more.


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[Wheel House Motorsports]

That was my thought because it's running in a very specific environment only at high altitude during a cold winter I should be able to get a little more out of the engine if not good bit more.


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You definately can! Helping the motor breathe that thin mtn air makes a world of difference! The guy who sold my old YZ at 300+ hours was laughing because it was still whooping up on brand new bikes.

What bike are you looking at modding?

 

[tillbuilt]

I had Junior build a Yamaha YZ450F motor for me in my Ferrari bike. It went 9 hours and blew up. Hes sent me a $3k bill for that rebuild and it it went 12 hours before it blew up again. He sent me another $3k bill and it told him, "no thank you". I spent over 10K with him for real power, but got 22 hours out of it and was down most of the season. I DNF'd 2 races and ruined my season points standings because of the unreliable motors he builds. He is very hard to deal with and does not provide good customer service. I had to get the shop owner next door to walk over and talk with him multiple times because he would not return my phone calls. I will not do business with him again.

I am trying a different big power motor builder this season. I got the bike on the dyno a few weeks ago and tuned this new motor. It did well and made great power. The oil filter did not have any where near the amount of metal in it as the Junior motors did after break in. I am hopeful that this motor will last and I can share a quality motor builder with you all. I will know after some time this season.

I keep reading about this engine builder and his work on hill climb, snowbike, arena bikes... anyone here have 1st hand knowledge or has used him for an engine build?

I am steering away from big bores and going with a straight engine set up....porting, cams, piston, dynotune.....

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[wwillf01]

So did you end up losing cranks?or just random issues...

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[tillbuilt]

So did you end up losing cranks?or just random issues...

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The rod and wrist pin pulled off the piston both times. It chainsawed through the cases and damaged the head both times.

 

[M5-]

If we are on the topic of where not to send your motor I had a similar bad experience with Thumper racing. Sent Travis my engine for a 520 big bore only to have it blow up in short order. Sent it back, paid again, blew up again riding dirt only in 20 hours. I finally tore it down myself and they had twice installed the wrong main crank seals, the bike was an 08 XC4 motor which has a one year only crank seal. The seals which were 2mm too large and they crushed them into the bore got eaten by the crank and went through the motor taking out the oil pumps. I still have the documents listing that they used the wrong part number in the engine and Thumper told me they didn't see how it was their problem and told me to go fawk myself, lesson learned. A-holes.

M5

 

[jrlastofthebreed]

Thats almost a case where you should have gotten a lawyer involved.... Well I guess now you know.....

 

[Brock hoyer]

I had Junior build a Yamaha YZ450F motor for me in my Ferrari bike. It went 9 hours and blew up. Hes sent me a $3k bill for that rebuild and it it went 12 hours before it blew up again. He sent me another $3k bill and it told him, "no thank you". I spent over 10K with him for real power, but got 22 hours out of it and was down most of the season. I DNF'd 2 races and ruined my season points standings because of the unreliable motors he builds. He is very hard to deal with and does not provide good customer service. I had to get the shop owner next door to walk over and talk with him multiple times because he would not return my phone calls. I will not do business with him again.

I am trying a different big power motor builder this season. I got the bike on the dyno a few weeks ago and tuned this new motor. It did well and made great power. The oil filter did not have any where near the amount of metal in it as the Junior motors did after break in. I am hopeful that this motor will last and I can share a quality motor builder with you all. I will know after some time this season.

I have had good luck with my junior motors!
From race to backcountry , they have been amazing
Maybe your doing something wrong ?

 

[wwillf01]

I wanted to update this thread. I put 120 hours on my Junior engine that ended up dynoing at 69 half oxygenated and half pump. Went through about 100 gallons of fuel through the season of hard riding and deep powder. Had some initial programming issue with it being lean ( don't know if the tps sensor was knocked at some point of install and shipment.. but other then that it was gas and go. So much overrev and pulling power through the rpms I really could not be happier. Putting a piston in and running it this next season. 9n another note I did the spring inserts for snowbikes from him also and they have been great after some oil adjustment.

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[dooman92]

Wwillf01, what engine was this? Would it run on pump premium?

 

[wwillf01]

This was the 18 sxf 450. I am going back to the dyno to see what I can get with pump and 50/50. I was told if the octane was accurate I could get any with pump at high altitude... but my dyno and tuning was based off u4 vp and pump. You could set up 2 maps for 2 fuel types.

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[wwillf01]

I would like to add you really feel the difference at my altitude tuned with oxygenated fuel.. it is a seat in the pants difference...

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[dooman92]

We ran oxy fuel on couple different trips on a 19 450 sxf and an 18 500. Both had vortex ecu's. Yeah, could feel the difference. But, spendy... What is compression ratio on your engine? Any idea what mods made biggest contribution to the increased hp?

 

[wwillf01]

So hard to tell what did the most. For me doing it all at once and the dynoing was very important. The piston is starkly different and reinforced for the power which I feel is important. Then cams, porting, get ecu and intake stack with k and n filter all work together. So that would be the first thing I would do. Then the Barker exhaust which is loud but added about 3 hp. I used a selkirk set up so I never had an issue with the k and n getting plugged or jammed because it stayed so warm in the engine compartment. We show 1 to 2 more hp than using a cage with a dry filter. I will do the top end over the next few weeks and can report back what everything looks like. I changed my oil and filter every 10 hours. I either used arctic cat 0-40 syn or vp 10-50 (only reason I get a heavy discount) syn or mixed half and half depending on the time of season. Everything else from bottom end to clutch was stock. The only thing I am going to change this year is going with a tunnel cooler so I dont have to take off the shrouds and the fan will not drain the battery as much when it is warmer out. I attached the stock and modified piston pic.

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