Help mounting thick tubing Trek Marlin 29er

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Nanfoe

Nanfoe

Member
Oct 15, 2016
39
5
8
Florida
I'm here with a mounting dilemma (literally). First of all this is the first time I'm going to install a CG on an aluminum frame. My knees can't peddle far anymore so time to convert the o'l hardtail to putt putt me along. I know iron/steel is the way to go (I have ferrous frames) but for now I have all the hardware for just one build so I would like to go with the only fully functional bike I have ATM which has trued rims and disc breaks. I have 2 different type forward mounts plus a universal on the way. I have a slab of 1/4 aluminum already bent, would aluminum on aluminum be as good as metal on aluminum? I'm just looking for some insight to mounting a aluminum frame. I have also the 27 tooth sprocket that goes on the disc hub. I plan on cutting to fit the CG chain. The motor is balanced and ported piston skirted and topped with an aftermarket head. Intake is port matched with the basic manifold/carb upgrade from stock. I have a big boy Reed with a Keihin clone on another CG ATM which I may incorporate to the green CG. Heres some pics of the break in bike and motors. Any help would save me some brain cells!! Thanks.
 

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ZipTie

ZipTie

Active Member
Jan 8, 2016
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Mpls Mn
As long as the mount is solid to the frame with no movement your golden. Cheap Chinese steel is softer than aluiminum as it seems anyhow. Lol. Just recheck tightness after some miles are racked up.
 
ZipTie

ZipTie

Active Member
Jan 8, 2016
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Mpls Mn
Nanfoe said:
Dam for steel to be softer than aluminium it has to be real crap. Thank you sir.
Click to expand...
Add the word brittle to soft also. LOL
On another funny note: There is a video posted on You tube somewhere where a guy remounted his engine using Duct tape after one of his Chinese mounts broke and he said it worked great.
 
ZipTie

ZipTie

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Jan 8, 2016
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Mpls Mn
Looks good, Any way we can see the other side of the bike too and a picture of how you mounted your engine if you get time. Exhaust looks pretty sweet.
 
ZipTie

ZipTie

Active Member
Jan 8, 2016
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Mpls Mn
Looks clean. Gee it's wedged in their pretty good, as in tight fit. My only concern is angle of the carb could cause a problem. I have one bike that has a angled carb also a and I worry about a lean condition it could cause as I am no expert on carb angle and any side effects it may cause. So I'm interested if and what problems it causes...if any? I would imagine their is a line one can't cross on it, what that line is I do not know personally. Some offset intake manifolds can rectify it but are they ever bad quality. I ordered one and it was full of bad welds with numerous pin holes in the welds, so I had it re welded, but it didn't help the angle much. Then I bought a double offset one and the mount flange was warped so bad I couldn't mount it. Anyhow does your bike run well?
 
Agreen

Agreen

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Feb 10, 2013
792
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Southeastern GA
A couple of small recommendations:

On the third picture in your last post, remove the studs in the engine and replace them with allen head bolts with some loctite.

The front mount is OK for now, but you may need something stronger in the future. Check eBay for a cnc front mount. They cost a little more, but it's way stronger than the Chinese u-bolt.

Edit: also you should insulate the white wire. If that grounds out, your engine won't like it too much.
 
Nanfoe

Nanfoe

Member
Oct 15, 2016
39
5
8
Florida
Yeah I'm waiting on a universal

http://www.ebay.com/itm/262519605050?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT

But I don't think it will fit as the front tube is so wide, maybe to the rear it would fit. I need different hardware and yes the align screws are a plus. The motor is almost done with break in, she sounds like a different type of 2 stroke, throaty, more vroomy than wingy. And she picks up just fine, she jumps to 28 mph and tops @ 37 mph but that was with 40:1, a #.70 jet, 32 tooth and stock muffler haven't tried the 27 yet. Dude at the bike store looked at the Trek and said with a 27 tooth I should have no problem doing 45 mph so I'm glad I have disc breaks. I couldn't get the disc ring off the rim to install the sprocket. My aligns kept slipping and I don't want to strip. I realy want to do as much work as I can myself. These are little things that always pop up and sooner or later every mech has to engineer something in a pinch. Thanks again gentlemen for your input.

Misprint: not 40:1 but 16:1
 
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S

Slogger

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Sep 8, 2014
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nohio
I don't even know how geared CGs generally do, but yours looks pumped up and snarly so I think it'll pull it.
 
ZipTie

ZipTie

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Jan 8, 2016
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I believe its a Felt frame of some type, don't know the model. Looks expensive and bad to the bone.
 
Nanfoe

Nanfoe

Member
Oct 15, 2016
39
5
8
Florida
The universal arrived today but it isn't going to fit this frame. I have a vitamin bottle that's a little bit less wide as my down post here for ref. I'm gonna take her to a place here localy and just let them do it. I'll craft on my other frames and just maintain this one when it's done. I'll post when she's ready.

:-||
 

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Agreen

Agreen

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Feb 10, 2013
792
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Southeastern GA
Man that does suck. Every one of those billet adapters are either 1-1/8", 1-1/4", or 1-1/2".

I'd fabricate my own, but that may be out of your reach to do. I hope it all works out for you!
 
ZipTie

ZipTie

Active Member
Jan 8, 2016
750
82
28
Mpls Mn
Nanfoe said:
The universal arrived today but it isn't going to fit this frame. I have a vitamin bottle that's a little bit less wide as my down post here for ref. I'm gonna take her to a place here localy and just let them do it. I'll craft on my other frames and just maintain this one when it's done. I'll post when she's ready.



would be very simple for any local machine shop to ream it out to the perfect frame size. They probably wont charge you more than 20 bucks to do it.
zip
Click to expand...
 
Nanfoe

Nanfoe

Member
Oct 15, 2016
39
5
8
Florida
I am an ex airport worker from the late 90's, I had so many hook ups from machinists to pilots letting me fly jump seat but I have turned into a introvert over the years and kind of never kept up with anyone. Sucks to have it and then loose it. There's a few shops around my town, I'm gonna slap together another build there that just needs a back rim which I'll try to get tomorrow so I can ride and look. Can't have the wife drive me around all the time!

Edit: I think I'll take a ride to Home Depot and see their hardware I might be able to swing something with this piece of AL here.
 

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Nanfoe

Nanfoe

Member
Oct 15, 2016
39
5
8
Florida
Oh and apologies here are the specs to the motor from BMW worked by Matt:

Balanced Bottom
Ported + Transfer Ports re-directed
Piston Modified for better gas flow
Cylinder Deck Lowered
6.0cc High Compression Head
15mm Intake Manifold (port-matched)
Heavy-Duty Aluminum Reinforced Exhaust Gasket
Copper-Coated, Port-Matched Intake Gasket
Bulldog Pipe (extra from Matt)
BH7 NGK
All hardware upgraded to grade 8.8
Running 16:1 87 octane

I will be adding in:

CNC Reed valve (align screws) with 20 mm Keihin clone
Rocket racing CDI
26 tooh sprocket

and a windowed piston I may try in the future.
 

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