|
|
Post by jimfroggy on Apr 23, 2020 2:48:58 GMT
I recently got my hands on a new set of carbs for the 400 which had been U/Sly cleaned, soda blasted and fully rebuilt, fit them to the bike and had a balance and dyno tune done just to put the final nail in.
Interested to see what readings anyone has gotten on a dyno for a 400?
Results for mine were 28.57hp @ 9400rpm with Max torque 18.59ftlb @7720. Graph said its showing good power through the whole range.
I wondered about the HP reading, given that Honda claim 40hp or so when new, but figured that's likely at the crank, so I was interested what anyone else had found on a dyno? For a 40 year old bike I can appreciate some power differencd and Ive not rebuilt anything top end or crankcase after buying the bike a year ago but all runs well so I'm not gonna touch it until necessary.
Tia
|
|
|
|
Post by buster on Apr 23, 2020 8:12:50 GMT
interesting stuff, I'd agree that the figures honda quoted would be at the crank (unless anyone knows different?) so I'd think the figures for your bike are about what you'd expect. a quick way to recover a few of the missing horses could be a de-coke of the cylinder head and re lap the valves, the only issue with that is when you come to actually take the head off theres a good chance that you will also disturb the barrels from their base gasket and to do the job properly that means barrels off too and a new gasket. then while your there you may as well check the ring gaps, maybe hone the barrels and fit new rings (gets expensive quickly). but as you say its running nicely, so probably a case of if its not broken dont fix it. again thanks for sharing the figures, dont think I'd be brave enough to dyno a 40 odd year old bike  |
|
|
|
Post by jimfroggy on Apr 23, 2020 8:37:55 GMT
Haha one guy was...
Yeah I don't like to poke the tiger. I'll do a rebuild one day, but for now I'm happy it's pulling well.
Made a massive difference with a nice clean Carby 👍
|
|
|
|
Post by earlystock on Apr 23, 2020 12:14:42 GMT
I have the 1978 road test of the 400 dream. I also have to workshop manual. The claimed horsepower was 43 I think, the actual according to the Motorcycle Mechanics road test was 36. I have attached their graph - maybe it might be good to compare with what you got. Generally drivetrain loss for chain driven bike is about 10% (as opposed to 15-20% for shaft drive), so if their numbers were at crank you would expect to see about 36 on a new bike - so not a million miles out (I had my 50hp CB550f dyno'd back in the day - as standard it was 39 at back wheel, with Yoshi, K&Ns and jetting it s about 46).  |
|
|
|
Post by earlystock on Apr 23, 2020 12:42:35 GMT
I have the 1978 road test of the 400 dream. I also have to workshop manual. The claimed horsepower was 43 I think, the actual according to the Motorcycle Mechanics road test was 36. I have attached their graph - maybe it might be good to compare with what you got. Generally drivetrain loss for chain driven bike is about 10% (as opposed to 15-20% for shaft drive), so if their numbers were at crank you would expect to see about 36 on a new bike - so not a million miles out (I had my 50hp CB550f dyno'd back in the day - as standard it was 39 at back wheel, with Yoshi, K&Ns and jetting it s about 46). |
|
|
|
Post by earlystock on Apr 23, 2020 12:43:06 GMT
I meant of course that you would expect to see 39 at the rear wheel
|
|
