Bros

[Anto72]

I have a 88 bros i cleaned the carbs and replaced the diaphragms and air cut off rubbers and new spark plugs and oil and filter change it will hit 150kph will different jets make any faster.it has stock exhaust and stock air filter as far as I know stock carbs and jets would like to hit 160 kph just for fun

[69Falcon]

An engine is an air pump, and you have to reduce restrictions on the intake and exhaust in order to make more power. An alternative is to go up one tooth on your front sprocket or down on your rear, but of course that will also slow your acceleration.

Adding bigger jets without removing exhaust restrictions won’t help you.

[ricksax]

Your stock exhaust muffler is very restrictive. You can achieve your goals with 1) rejetting richer, 2) a free flowing exhaust cannister [Fuel in England still makes them.] and 3) a smaller rear sprocket. I am running an aluminum Vortek rear sprocket with 41 teeth. That gives me about 4,000 rpm at 60 mph. Of course, it is slower off the line.

Hawk GT650 Exhaust MED.jpg

[Anto72]

Thanks for the advice guys I will definitely be looking at a new exhaust for it

[ricksax]

Just a note, FYI. The Hawk is special in that you can replace the rear sprocket quickly without removing the wheel or hub. Just loosen the chain eccentric, lift off the chain, and replace the sprocket. Re-adjust, not too tight.

[Anto72]

Thanks for that I had a look at the cush rubbers they are hard I presume they should be a little bit soft to take the strain

[ricksax]

The check for worn cush rubbers is: try to rotate the chain hub in either direction while the rear wheel is stationary. If it will move more than 1/8 inch (0.125), then you really need new ones. When they are fresh and tight, the hub will barely move at all.

[Anto72]

I have new ones on order from the Netherlands. No harm in changing them I really haven't rode a bike in 30yrs so getting back to it wanted something that wouldn't kill me as my last bike was a rg 250 gama mk 1 popping wheelies at 80mph going into 3 gear those were the days and 30kg lighter

[6]

I have new ones on order from the Netherlands. No harm in changing them I really haven't rode a bike in 30yrs so getting back to it wanted something that wouldn't kill me as my last bike was a rg 250 gama mk 1 popping wheelies at 80mph going into 3 gear those were the days and 30kg lighter

Those old 2 strokes are brutal. Dmitry has a Gama. Wont let me ride it, but he does have it, so thats cool...

[Dmitry]

It will never be a Gamma (maybe it can match HP of 250 but not weight) but you got to get a good slip on muffler if you want to get past 160kph, exhaust and jetting should get you at least 10 HP gain vs stock. IIRC the Dyno numbers from stock bikes back in the day were 37-39 HP, you should be over 50 once it's uncorked and jetted.
you can get to 70-75 but you might need to take out the second mortgage on the house to get there.
Hawk will never be as exciting as RG, my 500 with Crawford pipes is maybe 100hp on a very optimistic Dyno, but my Hawk will run circles around it on a tight twisty road, it's much better chassis, just need some suspension help: modern fork and longer shock

[Anto72]

Thanks for the reply will be on the look out for an end can what type of jets will fit stock carb also what size are the clutch springs just got a bag of goodies for it new cables clutch and Speedo and couple gaskets and fork seals from a bloke on advert.ie great price for them ohh ye clutch plates in it as well 6 is that what it takes.?