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Big bore?


Qwik

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With having blown the motor on my Bandit Sidecar rig. I’m going to do a Big bore build. Does anybody have experience with either the APE or Holeshot kits? Anything to avoid? Any tips, tricks,? Any help would be appreciated guys

Edited by Qwik
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I can understand why you want to go big bore on the replacement engine for you outfit,but imho I think for your application I would stick to a stock type rebuild,as all the big bore kits seem to hike the compression to around 12/13:1 which with the added load of a chair may be too much, if I were to make any mods it would likely be to find some gsx1100 f cams and lower the gearing to increase the mechanical advantage and keep the rpm in the sweet spot of max torque and hp . Just my opinion and as ever your ride your dime your choice (y)

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Holeshot and APE have both been doing it for a long time. Holeshot probably has more experience with the bandits and doing mild street tunes on them. Give Holeshot a call first and see what they recommend, APE is good for machine work and any parts that Holeshot doesn't stock. I agree with DAZ, stay away from doing a crazy high compression build. Nothing wrong with going with forged pistons, but use a base gasket to keep the compression reasonable for using pump gas.

Years ago a took a friend's bandit with a 1216 kit from Dale Walker for a test ride, big bore, lumpy cams, exhaust, and jet kit. Tons of mid range power, and a nice lumpy idle like an old muscle car.

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Well after about an hours worth of conversation with Dale Walker on the phone. I have a set/kit of pistons on the way. Cylinder is already been shipped to the machine shop to be bored. Cometic head gaskets on the way. Should be around 11 to 1 compression. The machine already has a Holeshot stage 2 set up on the jetting/pipe. This thing ran good before. It’s gonna run really good now

Edited by Qwik
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  • 5 weeks later...
On 9/27/2023 at 2:10 AM, DAZ said:

I can understand why you want to go big bore on the replacement engine for you outfit,but imho I think for your application I would stick to a stock type rebuild,as all the big bore kits seem to hike the compression to around 12/13:1 which with the added load of a chair may be too much, if I were to make any mods it would likely be to find some gsx1100 f cams and lower the gearing to increase the mechanical advantage and keep the rpm in the sweet spot of max torque and hp . Just my opinion and as ever your ride your dime your choice (y)

Turns out it’s only up to 10.8 to one. 81 mm bore. Still curious if I need to do more cooling. Should I be replacing the head stud bolts with new? Any other ideas?

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2 hours ago, Upshotknothole said:

You could always swap out the stock oil cooler for one a bit larger. The GSXRs always came with larger coolers than the bandits.

It is mandatory on any OSS bike that a larger (preferably aftermarket) oil-cooler with fancy fittings is fitted, and for oil cooled bikes whenever possible, an additional head cooler too :).

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  • 2 months later...
10 hours ago, Qwik said:

Well finally took the time to open up my Engine.  Now I need to figure out why that cylinder went lean.  Had to be over 1150° to melt that piston like that

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That ain't lean! I'd say it was quite rich possibly excessively! Witness the 'wetter' crown / valves and the cleaner appearance. The damage is detonation - see the spotting / pitting around the edges of the chamber on the head. Head doesn't appear to be massively skimmed but difficult to tell - what did the plug look like (if it survived)? Possibly leaky float valve & excess fuel = detonation? Piston crown looks well thin with some cracking but whether that was pre or post failure would be a guess! Sidecars are a strange breed - high rpm + high load for long periods - they usually kill gearboxes and being fully enclosed cooling is usually a big issue as cooling ducts add drag - I am assuming this is a racing sidecar?

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It’s a Street rig. Mostly used for riding long trips and sometimes for rippin twisties.  When the failure occurred I was at about 55 or 60 mph on the highway. Headed home from a 2300mile road trip. 40 miles from home it did this. Not heavy revs and a fairly light load in the sidecar (clothes and camping gear) the whole outfit weighs less than 750lbs empty

 

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Edited by Qwik
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  • 3 months later...

Motor is done. 81 mm bore, 1216 cc. 11.2 to 1 compression. Well the head was off we redid the valves. Made sure everything was good. Cleaned up real nice. Trying to figure out jetting. I will be doing a lot of trips to sea level and although I live at 7900 feet elevation. I think I would rather have it jetted for sea level. Trying to get this thing dialed in for long road trips. Nice thing with the tub as I can Carry a tent, a cot, sleeping bag, nice size cooler. And all the goodies

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