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I bought a 1978 Honda Hawk T2 about two years ago. It was in perfect condition. It's 400cc, great starter bike for me considering I've never ridden a motorcycle before. Unfortunately it went downhill because I have no mechanical skills whatsoever and didn't have the money to just keep taking it to the shop. I'm learning now but still have a few questions.

I'll keep it simple. It's a 400lb bike with a 400cc engine. I've been using it for an in town bike (work, school, leisure), and it's worked amazing. It has an oil leak which I'm going to fix (get someone to fix it), along with start up issues. I get in top gear around 35-40mph running around 4000RPM's, and it's running high RPM's from then on. I've cruised at around 75mph for about 20 minutes and it was hitting around 7000-8000. It redlines at 10,000 RPM's.

So my question is, is that healthy for the engine. I know I shouldn't be redlining it. But I'm moving to Dallas and I don't have another vehicle and I wanna know if it's alright to at least drive 70mph cruising at such a high RPM level. Maybe changing the final gear ratio will help? changing the tooth count on my sprockets? I've read several times of that helping but I don't know how nor the exact information I need to go about doing so.

Sorry I wrote so much, it's my first bike and I feel she deserves the right treatment after I neglected her well-being for so long. Any information would be awesome.
 

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Running toward the higher end of the RPM scale won't hurt the engine as long as everything is working properly. The fuel mileage may decrease a bit.
 

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Just keep in mind that if you do change the sprokets to a higher gear ratio, you will loose low end torque. If you go too severe (which would have to be really severe), you would have to push start from a dead stop.

One thing you could do is change the ratio just for the move, go with the flow of traffic and not worry about the speedo, and then change it back when you get there.
 

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remember too that smaller engines need to spin more to accomplish the same amount of work.

That in mind I'd go up one tooth on the front sporcket anyway because it can handle it. Back in 78 the speed limit for the nation was 55 mph so the bike is geared to be in good power at that range. Stepping up one or even two teeth on the front will put it more into the era now with the 65 mph limit.

As a generalization you will drop about 500 rpm per tooth in the revs. You will need to keep it in mind when running in the 35-45 mph range, probably running a gear lower. I keep my bike at about 3500 rpm when riding in general. I seldom drop below that except when near coasting in town. The reason is throttle response. At 3500 rpm I am right at the base of the good power.

The Honda 400 can handle the rpm no problem. My 550 does about 6500 at 75 and I'm good with that. I'm more concerned with the two characteristic buzz zones on my bike. One at bout3900-4200 rpm and again about 5900-6200 rpm. It was characteristic and noted in the old bike tests. I'm at the biggest front sprocket I can get right now, I am going three to five teeth less on the back to change the rpm range at speed. 50 is right in the low range buzz and 70 is right at the upper range buzz.
 
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