Monza rebuild options?

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Bensmith225
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Recently had an asso piston fail in my monza 225 which took out the cylinder spigot on the inlet side and debris made to the combustion chanmber and bent my conrod. So it’s time for a steel liner and new conrod. Question is do I have the liner to suit a 71mm piston or stick with the standard 70mm? What conrod length would be best on my 60mm crank? I was thinking 110mm but a lot of people seem to be going longer. And was also thinking of a tune on the barrel while it’s all to bits. What difference does extra boost ports have on the performance versus the standard single one? Just thinking of getting it all done while it’s in bits


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bazza3004
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Running a Darrell Taylor built 60/115 on mine
Bensmith225
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What does the extra rod length achieve? I understand the 110 makes it easier to set the port timings but I’m curious if a longer one makes it smoother or not


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holty
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yes a longer rod does allow you to adjust port timings by packing the cylinder up, i have also read an article that explains how the longer rod gives more torque compared to a short one, its down to the angle of the rod, longer rod less angle, i suspect it does make the engine run smoother as well, my rotax has a 125 rod and does run fairly smooth considering its a 64 stroke and 76 bore
Bensmith225
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Right ok I’ll maybe look into a longer rod then. I suppose it can’t do any harm. What are people’s thoughts on port layouts. Having it steel lined gives me a blank canvas to start with and seeing it’s a v1 monza which I’m told is a tuners wet dream due to all the meat on the barrel I wanna make the most out of it


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GTFOMWSC
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Bensmith225 wrote: Wed Oct 17, 2018 10:57 pm Right ok I’ll maybe look into a longer rod then. I suppose it can’t do any harm. What are people’s thoughts on port layouts. Having it steel lined gives me a blank canvas to start with and seeing it’s a v1 monza which I’m told is a tuners wet dream due to all the meat on the barrel I wanna make the most out of it


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I would speak to someone who has tuned one with success and go on his advice before getting it lined or a longer rod in it.Chris Sturgess has had really good results with these get the tuners input first he may suggest differently to steel lining it for example you may know who you want to tune it already but seak his advice before going ahead with anything first.
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Bensmith225
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I’m getting Harry Barlow to do it as he only lives down the road from me. there isn’t any option other than steel liner due to the damage caused when the piston skirt fell to bits, I was just looking for any other input from people with the same cylinder


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GTFOMWSC
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Bensmith225 wrote: Thu Oct 18, 2018 12:17 pm I’m getting Harry Barlow to do it as he only lives down the road from me. there isn’t any option other than steel liner due to the damage caused when the piston skirt fell to bits, I was just looking for any other input from people with the same cylinder


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I have a Monza tuned by Harry can get 80mph out of it max i purchased the scoot with it already done now rebuilding the engine after 1 years use as rings wore down very quickly(under 1000 miles) nice guy is Harry.
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Bensmith225
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Well I’m hoping for a bit more than that as I’ve maxed it at just over 90 on gps as it stands. Being the v1 it apparently had better porting to start with and Harry says It doesn’t need tuning but I know there’s room for improvement in there as it struggles to full Rev out unless the conditions are just right


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GTFOMWSC
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Bensmith225 wrote: Thu Oct 18, 2018 3:48 pm Well I’m hoping for a bit more than that as I’ve maxed it at just over 90 on gps as it stands. Being the v1 it apparently had better porting to start with and Harry says It doesn’t need tuning but I know there’s room for improvement in there as it struggles to full Rev out unless the conditions are just right


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good luck on it i have both Monza versions Harrys tuned one is 24bhp top end 80mph and that's screaming, the other gets to 85mph top wack(well maybe a bit more if i sit with my head on the headset virtually) 28bhp both are taken to 230cc. The standard has a Harry crank in it 110 rod the other is on a misano case with a 110 rod as well but the larger crank both accelerate really well both using the AF close ratio 4 speed box both using 3omm dellorto carbs from camlam although the super has a powerjet version.The super has a TSR Darrell Taylor converted pipe while the standard has a converted JL pipe.I like riding both of them equally but they aren't as fast as people reckon they are 5 speed boxes will improve them that would be the next step one thing i would say is even giving them full throttle which i do often on them they don't feel like they'll blow(famous last words that!).
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