most jap 400s that were speed restricred thet went to the uk had a restrictor in the speedo as karitane pete says ,this would be my first thought ,replace with one from an aussie bike and try that.if that doesnt work try talking people who bring other grey imports in and they should be able to point you in the right direction.
i believe that 400s of the time had a simple pin in the speedo that caused the rev limiter to cut in at 180kmh no matter what gear you were in ,or revs you were doing.hope this helps.
"R710 engine's were used in the 88/89 750's. I need to know which model your bike is, J or K and which local the bike is for i.e. japan, europe, switzerland etc
If your bike is a J model it shouldn't have any restrictions but they often do, voluntary restrictions to protect the industry. Igniter box minimum but maybe (probably) cams and carbs as well.
If it's a K model there are at least 2 different versions that I know of but the only differences are the gearbox's, 3rd and 5th gear.
If it is a K model this makes it an 89 model year, the year the Japanese introduced the internal Speed restriction of 112.5mph or 180kph(Japanese local only) Suzuki enforced this using a restricted Ignition, My RK had this restriction. I have also seen Japanese grey imports from 1989ish with 34mm carbs, different cams and restricted Ignition box's.
The only R710's that I know of that might be restricted are Japanese or Swiss model. The Japanese model should have a red light marked as 'speed' that comes on at 55mph and the Swiss has an emission control sysem."
found this quote on another post
hope it helps
(i think it was sickpup,all hail!!)
HI Skilo54 thanks for the info, my bike is a Japanese bike with the speed light you spoke of, so if you have any more info on these i'd be greatful. I dont need the speed on the road but when I do a track day, well you know how it is. Thanks mate.
hi all, any idea whats the top speed of a 88 slingshot (J), i have a restrictor thats cuts out at 180km/h. also want to put on a after market exhaust, any suggestions which will give me more horse power? thanks