Project Punsun
Moderators: Dan J, Diesel Dave, Crazymanneil, Stuart
Project Punsun
As I noted in my introduction,I am the proud owner of a 2007 year Punsun which I acquired last year. (Brand new). Can anyone tell me if the starter motor is suspect on this year/model or should it be OK? (This engine hasn't been started yet). I spent some time looking into arranging the engine Guzzi style, but came to the conclusion that overcoming the reduction in the primary drive in both Guzzi and BMW gearboxes was more trouble than it was worth. So having decided to go down a more conventional route I have acquired an RGV 250 six speed engine/gearbox assembly. I'll replace the crankshaft with a jack shaft, this will be driven at twice engine speed which should result in being able to use a 'normal' sized rear sprocket and obtain (without too much fiddling about) a cruising speed of 108 kph at 3000 rpm and a top speed of 132 kph at 3600 rpm. I've hit the jackpot with running gear, etc., a 1986 GSXR 750 minus only the motor and gearbox, all for the princely sum of $200! (Mind you, it did cost me about $100 in fuel to pick it up!) Probably the only thing I won't use will be the frame itself - a 25 year old aluminium frame and a diesel engine equates to a high risk of frame cracking to my way of thinking. So having accumulated all the major parts it is time to design a frame to hold it all together. I'll keep you posted
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alexanderfoti
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Re: Project Punsun
Sounds great!
Which engine is it? is it the twin cylinder punsun?
Which engine is it? is it the twin cylinder punsun?
Re: Project Punsun
Yes, it is the 22 hp. V twin engine. Have you had any experience with this engine?
Cheers, Brian
Cheers, Brian
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alexanderfoti
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Re: Project Punsun
Cool!
I dont have any experience with it, but I will be looking to get one for my next build, 22bhp should be enough for 80mph at least, and I cant imagine the fuel economy is much different!
I dont have any experience with it, but I will be looking to get one for my next build, 22bhp should be enough for 80mph at least, and I cant imagine the fuel economy is much different!
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DieselFly
- I luv the smell of Diesel...
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- Location: Kingston Ontario Canada
Re: Project Punsun
Hey Brian
I have a 20hp Punsun in my bike. There has been some problems with the early 22hp and 25hp breaking cranks search the old engine posts you will find it. I bought my engine in 2009 and the starter was the new type and had been around for only a short time. These are stationary engines so try to run it between 3000-3600rpm this is where they are balanced. I have over 3000 miles on mine and the only problem has been a weeping head gasket and a broken spring on the throttle gizmo that hooks to the arm that goes into the engine for fuel control. I run a CVTech CVT transmission. I get about 74mph flat out and when ridden for milage I get up to 115mpg normal riding flat out blowing black smoke and such I get 95-100mpg. Oh and they sound great with straight pipes
Sean
I have a 20hp Punsun in my bike. There has been some problems with the early 22hp and 25hp breaking cranks search the old engine posts you will find it. I bought my engine in 2009 and the starter was the new type and had been around for only a short time. These are stationary engines so try to run it between 3000-3600rpm this is where they are balanced. I have over 3000 miles on mine and the only problem has been a weeping head gasket and a broken spring on the throttle gizmo that hooks to the arm that goes into the engine for fuel control. I run a CVTech CVT transmission. I get about 74mph flat out and when ridden for milage I get up to 115mpg normal riding flat out blowing black smoke and such I get 95-100mpg. Oh and they sound great with straight pipes
Sean
Finished and riding 1975
CB500t Turbo Punsun powered
hardtail.
CB500t Turbo Punsun powered
hardtail.
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alexanderfoti
- Site Admin
- Posts: 1290
- Joined: Fri Jul 15, 2011 4:22 pm
- Location: London
Re: Project Punsun
It does sounds like a good engine/project.
My eventuality would be to build a diesel bike with the v2 diesel and turbo it. That would be awesome!
My eventuality would be to build a diesel bike with the v2 diesel and turbo it. That would be awesome!
Re: Project Punsun
Hi Sean
I have been having a bit of a look at the posts for some years now, particularly in regard to Punsuns, thats why I wanted to know when the crank problems were overcome. I have a suspicion my 2007 build motor may be suspect. The general idea is not to exceed 3600 rpm, and to be able to maintain a reasonable cruising speed (about 105 kph - our speed limit is 100 kph) at 3000 rpm. I am impressed with your project, it is simple, it looks good and it works well. (Sounds good on that U tube video too!)
I considered using a CVT at one stage, but we do not have too many 'flat' roads here in the North Island, besides that the other persuading factor was the small matter of a large price for CVT's here as opposed to second hand gearbox units!
Cheers, Brian
I have been having a bit of a look at the posts for some years now, particularly in regard to Punsuns, thats why I wanted to know when the crank problems were overcome. I have a suspicion my 2007 build motor may be suspect. The general idea is not to exceed 3600 rpm, and to be able to maintain a reasonable cruising speed (about 105 kph - our speed limit is 100 kph) at 3000 rpm. I am impressed with your project, it is simple, it looks good and it works well. (Sounds good on that U tube video too!)
I considered using a CVT at one stage, but we do not have too many 'flat' roads here in the North Island, besides that the other persuading factor was the small matter of a large price for CVT's here as opposed to second hand gearbox units!
Cheers, Brian