Tom Morgan YZ315 Stroker (Red Bull Straight Rhythm)

Yz229
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Yz229 9/25/2018 2:43pm
9/25/2018 2:43pm
0-500ft ASL (San Diego)

Did not go leaner, went much richer per Tom Morgan

185 Main
N3EW #2
55 Pilot
1-1/2 out on AS

Redline oil 48:1
15/50 gearing

It ran extremely well! I think jetting is spot on actually.


Also took a field trip today...


2
Yz229
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Yz229 10/2/2018 3:17pm
10/2/2018 3:17pm
Final upgrade for a while! Not really anything else to do. Runs very strong. Even with 11-oz FWW and taller gearing it still hits hard and pulls forever.


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cdoggy81
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cdoggy81 10/2/2018 3:54pm
10/2/2018 3:54pm
Nice on the suspension!
As for the jetting I always thought you went leaner on the main for a big bore bc it had a stronger intake charge / pull. The more moving air through the carb (because of the increased displacement) provides a stronger vacuum signal to pull more fuel through the jet. Same for major porting. That being said I don’t have a dyno in my office nor do I do it for a living... Smile
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Yz229
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Yz229 10/2/2018 4:41pm
10/2/2018 4:41pm
I asked Tom Morgan the same question a few weeks ago and this was his response...

"A big bore pulls more air volume thru the intake tract and also requires a smaller throttle opening to create the same torque. This raises the vacuum in the carb which causes a larger pressure differential between the float bowl and the venture. This pulls more fuel thru the same size jet. The A/F ratio is the same but people mistakenly believe that it is leaner because of the smaller jets. The main change that you will make when increasing the engine displacement is in needle clip position and air screw setting. The main jet stays very close to the same as with a smaller bore.

Thank you,
Tom Morgan"
cdoggy81
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cdoggy81 10/3/2018 7:23am
10/3/2018 7:23am
“The main jet stays very close to the same as with a smaller bore.”
Per Toms own words a 185 main is nowhere near stock for sea level. I would think around 175-178 would be more in line.
Yz229
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Yz229 10/3/2018 8:50am
10/3/2018 8:50am
cdoggy81 wrote:
“The main jet stays very close to the same as with a smaller bore.” Per Toms own words a 185 main is nowhere near stock for...
“The main jet stays very close to the same as with a smaller bore.”
Per Toms own words a 185 main is nowhere near stock for sea level. I would think around 175-178 would be more in line.
MXA recommends 180-182 MJ with aftermarket pipe and reeds at my altitude. Tom recommended 185 to play it safe. Could run 182 easily I'm sure. Either way, it runs really well with the 185. With the head modified to run the crappiest 91 octane gas and with the squish could probably run a pretty wide range of jetting.
cdoggy81
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cdoggy81 10/4/2018 7:49am
10/4/2018 7:49am Edited Date/Time 10/4/2018 7:51am
I just checked PC’s website & they recommended 178 stock & 175 with a pipe.
https://www.procircuit.com/jettingspecs2.htm
When reading the fine print this was with VP C12 (which is 112 octane if I remember correctly) so that is prob why they could run “leaner” than what MXA recommended. That being said I think what you mentioned “With the head modified to run the crappiest 91 octane gas and with the squish could probably run a pretty wide range of jetting.” is really the important part part! Smile
At the end of the day if it runs good for you then go with what works for you & your bike right :-)
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Yz229 10/4/2018 8:09am
10/4/2018 8:09am
Not only that but porting which I forgot to mention. I think I asked what a ported YZ250 he does runs for jetting and it has a large main as well.
Yz229
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Yz229 11/15/2018 6:24pm
11/15/2018 6:24pm Edited Date/Time 11/15/2018 6:27pm
Bottom end needs a rebuild. Is there a better time then now to get the cases matched to the top? Will be 76mm stroker, with modified bottom end. Will now be a YZ315. Why? I'm 33 and already having a mid-life crisis. Also my first baby is due in April-May so need to get all the bike fun before all my money is gone.

Pics to follow later.
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SeaClassExpert 11/15/2018 6:59pm
11/15/2018 6:59pm
Yz229 wrote:
Bottom end needs a rebuild. Is there a better time then now to get the cases matched to the top? Will be 76mm stroker, with modified...
Bottom end needs a rebuild. Is there a better time then now to get the cases matched to the top? Will be 76mm stroker, with modified bottom end. Will now be a YZ315. Why? I'm 33 and already having a mid-life crisis. Also my first baby is due in April-May so need to get all the bike fun before all my money is gone.

Pics to follow later.
I hear nothing but great things about Crankworx, but I used a local builder up here in norcal when i had my husky's crank re-built. Crankwox may take some time to get it back to you, but I've heard is work is up there with the top in the industry, if not THE best.
Yz229
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Yz229 11/16/2018 7:40am
11/16/2018 7:40am
Tom Morgan will actually be building it, along with flow benching reed cage and carb. He uses stock crank, balances it and uses OE Yamaha rod kit since OE is proven reliable.
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mattyhamz2
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mattyhamz2 11/16/2018 7:42am
11/16/2018 7:42am
Bummer about the lower end man... Congrats on the incoming little one! Boy or girl?
Yz229
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Yz229 11/16/2018 7:50am
11/16/2018 7:50am Edited Date/Time 11/16/2018 7:52am


To answer your question about boy or girl, just did a gender reveal the other day. It's a boy!

Bottom end is ok, but was looking pretty bad when I put on top end. Just wanted to do this before it grenades itself.
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mattyhamz2 11/16/2018 8:08am
11/16/2018 8:08am
Yz229 wrote:
[embed]https://photos.google.com/photo/AF1QipNVwh3xX4gyxyqzjWCoXAwsmumkIxNZiYpFD2kQ[/embed] To answer your question about boy or girl, just did a gender reveal the other day. It's a boy! Bottom end is ok, but was...


To answer your question about boy or girl, just did a gender reveal the other day. It's a boy!

Bottom end is ok, but was looking pretty bad when I put on top end. Just wanted to do this before it grenades itself.
Awesome man! Congrats! It's going to be a lot of fun. Kids are a blast
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Yz229 11/17/2018 10:30am
11/17/2018 10:30am
Thank you! Not going to lie, excited to be having a boy!
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mattyhamz2
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mattyhamz2 12/5/2018 12:56pm
12/5/2018 12:56pm
Yz229 wrote:
Thank you! Not going to lie, excited to be having a boy!
Time to start saving for a PW50 Tongue

Any plans for the old desert tank that came on the bike?
Yz229
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Yz229 12/5/2018 4:47pm
12/5/2018 4:47pm
I know someone has PW50 for cheap, might try to snag it eventually.

Desert tank will be used for dunes and some of the longer rides.
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Yz229
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Yz229 12/21/2018 12:52pm
12/21/2018 12:52pm
Toms is getting close to assembly on 315, just waiting on YZ250X 5th gear. He is porting for slightly more top end then his usual build.

Also just added a brand new 304 silencer in exchange for the R304. Cut 8 1" inch holes in airbox and going to use this to help seal it up a bit better!
https://www.amazon.com/gp/product/B0738M9P7S/ref=ox_sc_act_title_1?smid…

Should be coming back together start of the year!



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Yz229
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Yz229 1/10/2019 10:17pm
1/10/2019 10:17pm
I've used the little unifilters in the past. Was looking at those vent things, but seemed a little spendy. Might be able to use the screen door repair for something else later.

315 is on the UPS truck now, should be here on Tuesday, along with Rtech tank and graphics. Hopefully will have it all back up and running by the end of next week.
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cdoggy81 1/11/2019 9:45am
1/11/2019 9:45am
I talked to him the other day & he was just finishing your 315 :-) Should be a rocket when done!

Sounds like you got the last Rtech kit too as everyone is out now. Who did your graphics for them?
Yz229
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Yz229 1/11/2019 10:11am
1/11/2019 10:11am
You getting some work done by Tom? Yes should be fast! Hopefully controllable as well.

Rtech is out of stock everywhere, so no Rtech for now. I literally was 12hrs too late! I already ordered the shroud graphics from Red Label, just like my old graphics but to match my old set. Would be using my old Cycra plastics.
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cdoggy81 1/11/2019 10:59am
1/11/2019 10:59am
Yep, hardest part was deciding if I wanted to keep it pump gas friendly or get the 2hp bump from the high comp head Smile

Sorry to hear you missed out on the rtech stuff. If you are interested I have a real nice xfun alum tank & shrouds I would sell you for about the same price. PM me if so.
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Yz229 1/11/2019 11:12am
1/11/2019 11:12am
I went with 50/50 on the 315, but I guess Tom only builds them that way. Had him go slightly more top end as well...not a low end type of guy. He said 58HP or more on this one. Also went with YZ250X 5th gear.

Can you send me xfun pic? Never heard of it. I already got shroud graphics, but may be interested.
Yz229
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Yz229 1/15/2019 12:56pm
1/15/2019 12:56pm
Here she is, 315 stroker!








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cdoggy81
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cdoggy81 1/15/2019 5:02pm
1/15/2019 5:02pm
I bet that thing will be a beast! I like the decomp pull on there too.

Did he bore that carb?
Yz229
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Yz229 1/15/2019 9:56pm
1/15/2019 9:56pm
cdoggy81 wrote:
I bet that thing will be a beast! I like the decomp pull on there too.

Did he bore that carb?
I think he did bore. He said bench flow carb and reed valve though.

Got it all together tonight, and it runs! Have a pin hole leak in coolant hose, and small gas leak. Will get those fixed and get a ride in hopefully this weekend.
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Yz229 1/16/2019 12:49pm
1/16/2019 12:49pm Edited Date/Time 1/16/2019 4:37pm
Here is the latest and greatest. Lost 10lb's and added 10HP...drilled washers!



Been raining pretty good here in San Diego, but took it for a quick 5min spin. It's fast! Might be a little rich though, so hopefully will get a good ride in soon.

cdoggy, I asked Tom about carb. Combination of hand porting and bore is now 41mm worth of airflow.
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