Puch/Murray build progress

I guess it's time to start a build thread on here...

I got the Murray frame from the EBay and decided to build a top tank GP styled bike. I had lots of parts left over from a maxi build and acquired some new parts along the way.

I (carefully) cut the rack off the back of the frame. It's still very straight and usable if anyone needs it!

I'm using the Honda headset conversion from puchshop but modified to accept tapered bearings. Honda MB50 forks and triple-trees. I had to cut about 15mm from the bottom of the head tube. The puchshop conversion is also for a maxi so I got some blue spring stock (18g thick) and wrapped it around the cups before pressing them into the Murray head tube. Fits like a glove!

I pretty much eyeballed the top tube after looking at lots of pics of different Magnum frames. Seems to look correct but I'm sure it's a little different. All the tank/seat mounts are not permanent so I can always switch things up in the future. I got creative with some seat clamps I cut out of the maxi frame.

The motor mount was slightly off kilter so I cut one side completely off and mounted the E50. I pulled it closer to center and welded it up. The back of the mounts were also boxed in for extra strength.

Re: Puch/Murray build progress

I had a robot swingarm from a maxi that I cut up and re-welded into a magnum style. My cousin laser cut some new axle plates for me. Measured out to be 15.25 inches. I braced the front of the swingarm near the mount as well.

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Im using some Sebac shocks I had. They measured out to be 320mm. They are a great length match for the Honda forks.

I purchased a Malossi MVR from treatland a while back and decided it would be a good fit for the Murray frame.

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Re: Puch/Murray build progress

The E50 that I had was in rough shape. I was using it on the Maxi I had. That bike was stolen some time ago and recovered with help of a Landsquids member. Thanks Chris! The perpetrator was actually riding it when he was caught. The metrakit "80" cylinder was toasted but somehow still ran. Gotta love the iron cylinder metras! I'm a fan.

When I finally tore down the E50 I saw the damage. The cylinder walls were badly scored and it had almost no compression. The bottom end looked fine but I still replaced everything. I did however keep the Rito crank just with all new bearings and seals.

When I originally got the maxi it was someone else's project and the E50 was already built. After tearing into it I saw that the case work was very poor. Terrible port matching and there almost no material outside of the transfers to make a good seal.

I ended up getting a new case and having it welded up before I did my own porting.

Re: Puch/Murray build progress

Here's the setup:

4 bearing case welded and ported then bead blasted.

Metrakit small port cylinder bored .8mm over (now 75cc)

Smoothed out the rough casting on the squish band and then bead blasted

Rito crank and rod with Wiseco needle bearing

All new bearings and seals

Trickmetric version 1.0 clutch with smoothed out spring holes. I had to clean up and debur all the edges. Using yellow springs. RC car throttle spring inserted into the crank hole to keep the starter plate away from the clutch. Works great.

Treats CDI set at 1.8mm BTDC. Pietcard 2041 CDI box

Dellorto 21mm PHBG DS "race", pretty sure it's a clone. Started with a 95 main and a 55 idle. W7 needle on second notch down. Using an old Motomatic intake tube.

Homoet 8p pipe

16x45 gearing (for now)

Re: Puch/Murray build progress

Got the back wheel mounted and spaced out. Lined up perfectly with the front sprocket. Running 2.75 Hutchinson GP front and back.

Still waiting for the front disc and then I'll work on the other side. Going to be using the GM 90mm idler pulley until I have time to machine a new hub insert.

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Re: Puch/Murray build progress

I'm using a magnum front faring I had but I made a plate from ABS and offset the headlight for a more GP/endurance look. I hacked up the Honda MB50 faring mount and made my own creation. Super strong and easily asjustable.

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I got some new controls with a remote brake resevior. Even with the Trailtech vapor there is enough room to mount the resevior inside the fairing. Threw on some nice Domino grips and called it good. Mounted on some EBay clip-ons it look darn good.

Re: Puch/Murray build progress

So far here is how it looks:

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Got a 220mm disc on the way. I will be using a dual piston from caliper. After that it should be time to road test!

Stay tuned...

Re: Puch/Murray build progress

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Front brake disc finally arrived. Need to make a bracket and get the correct sized line.

Re: Puch/Murray build progress

Too bad there isn’t a forum dedicated to builds..some are in the Gen forum, some are here in the Performance forum what chaos

Re: Puch/Murray build progress

Wow very nice

Re: Puch/Murray build progress

Looks great so far! What are you doing for tank? Looks like you had something under the fairing in a couple pics.

Re: Puch/Murray build progress

Im using a murray tank I got from Lucky2Strokes. I cut out the cap/filler section and closed it up with a plate. The tank now hangs upside down under the top tube. I had to move the petcock bung to the bottom and I welded a 30mm filler neck on top. I still need to finish the welds to seal it up and pressure test. The seam line on the tank lined up perfectly with the MVR tank/seat.

Re: Puch/Murray build progress

Haven't updated in a while.

Pretty much done with the Murray. Still messing with carb tuning and timing. It's been cold in Sacramento so I may take a break until it warms up a little.

I have been going through hell trying to find a decent head gasket. I've finally found a solution in an aluminum hobbit 47mm gasket I had to modify.

Jetting so far for the 21mm PHBG is 42 idle, 100 main, W7 needle 2nd clip down.

16° advance timing with the pietcard 2041.

16x45 gearing

Runs strong and accelerates very fast but...as soon as I open up to WOT it hits a wall and will not accelerate at all. It's not bogging it will just not go any faster. I have to back off throttle for it to go faster. I've checked and double checked for leaks and there are none. Is this timing related? Do I need to downjet?

Thanks to anyone who has suggestions.

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Re: Puch/Murray build progress

Brandon Weiss (aka B-Man) /

What does your plug look like? How close are you to top speed when this happens?

I'd guess you're maybe a little rich...

Could be a number of other things though.

Re: Puch/Murray build progress

Plug is dark brown, not black. Not oily. Running 44:1 mixture.

It will get up to 40 real quick then creep slowly up to about 46. That's the fastest I've gone so far. My trailtech vapor says 10,000 rpm give or take. It jumps around a little. I've got to mess with the wire wraps around the plug wire.

I can get up that speed with 1/2-3/4 throttle but as soon I open it all the way it will sound like its struggling and maybe lose a few mph. I've ridden around at different speeds and it's always the same thing. Even cruising at 30 seems effortless but as soon as I do WOT it just stops accelerating.

Re: Puch/Murray build progress

Mikey Antonakakis /

Seems like your main jet is off. Try upjetting, or just richen the needle to see if it gets marginally better.

Re: Puch/Murray build progress

Brandon Weiss (aka B-Man) /

46mph with 16x45 gearing is pretty damn good. Youre very close, just mess with the main jet a little.

Upjet first by a couple numbers to see if it gets worse. If it does, go 1 or 2 jets lower than what you had.

Re: Puch/Murray build progress

Aaron Ward /

Try points or a better CDI.

Re: Puch/Murray build progress

timothy rendall /

that is a very nice ped you've made there :) can i ask what front forks are you using ?

( i also hit a wall @wot so i'd like to know how you get on keep it up :) )

Re: Puch/Murray build progress

Thanks very much. Honda MB5 forks and triples.

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Nice day for a ride! Fixed all my air leaks and still tuning this damn PHBG.

Right now I'm at 100 main and 42 idle. Needle 2 clips down.

Currently hitting 48.6 mph with 16x45 gearing. Fastest so far.

Rpm flutters from 10,500- 10,800

I'm wondering if the Homoet 8P just won't rev any faster? Anybody else with a big e50 kit running this pipe?

I may try to advance timing a little. It won't get over 380 f even with sustained WOT.

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Re: Puch/Murray build progress

damn, gold snowflakes look amazing. now i wish i had done my five stars black and flakes gold and not vice versa

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8p revs to the moon. Drop to a 15 front to be able spin out faster and higher. Didn’t read what ignition but with a good cdi time correctly you shouldn’t have high rpm issues. I’ve hit high 13k’s with a 8p on gila and mk80.

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are the small ports more conservative intake and exhaust? i've never built one, but they look smaller. could be holding it back from what a big port MK80 would do.

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You’re not getting hot because you’re probably very rich, Pull that that double sponge off of the carburetor and run a real filter (k&n) or no filter,

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Thanks I'll give that a try.

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I think it's the same size in./ex. as the big port kits.

Transfers are smaller but I've done lots of work to them.

Re: Puch/Murray build progress

> Graham Motzing Wrote:

> -------------------------------------------------------

> are the small ports more conservative intake and exhaust? i've never

> built one, but they look smaller. could be holding it back from what a

> big port MK80 would do.

If memory serves port timing is the same, the last one I ran it on was a small port with lots of porting (transfers were shaped to match a case that was previously matched to a polini, so I'd call it a medium port).

> Ken Roff Wrote:

> -------------------------------------------------------

> You’re not getting hot because you’re probably very rich, Pull that

> that double sponge off of the carburetor and run a real filter (k&n) or

> no filter,

(Uni-)Pod filters are the best!

K&N suck and are expensive; no filter literally sucks (everything into the engine). I run the big uni-pod foam filters on most of my bikes unless they have a velocity stack with a rock catcher. Ken, don't go chasing water falls....

Re: Puch/Murray build progress

Joe Schuitema /

You mentioned it's timed to 16 degrees, but not what the final advance was after it retards it. Can you check the timing at say, 8000 rpm? It may be a bit too low.

Re: Puch/Murray build progress

I'll check again. I was planning to advance slightly. Metrakit instructions say 18 BTDC.

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