dnseal
CapnGil
Agreed XSChris, strange though how they would drop (restrict) the HP by 11 hp from 38 to 27. I know the early post 70 muscle cars fudged the numbers to get by insurance issues, but bit did mortorcycle have to go through the same issues in the late 80's?
I did some comparisons with available specifications as printed in the Yamaha's Service manual Part# LIT-11616-XS-42 which has models from 360 (C-D) through 400's (D-J) and came up with the following. There is not enough of a difference to make up a 11 hp (24%) difference between the models.
The following is a quick review and jumping from page to page is hard on these old eyes, so accuracy is 98%;
compression the @ 9.3 to 1, with only the 400D being 9.2 to 1
Bore stroke same
Intake and Exhaust Valve sizes same
Cam lobes, lift, duration the same
Timing at 10 DBTDC at 1200 RPM same
Carbs had minor difference in pilot jets but the format of document made it difficult to verify this time around. I will research more later.
Exhaust? No way to determine flow restrictions, but again most likely minimal and nothing to cause a 11 hp difference.
Conclusion so far; put on and older carb or do some minor jetting and gain 11 HP.... smile. I really think this is a corporate/printing/reclassification type of error. I still refuse to believe the same engine can loose 11 hp without some sort of governor, rev limiter, ristrickor plate, etc doing so and if there is one where is it?
Be Well
Gil
As you can tell I'm ot on of those "climb the mountain because it's there" kinda guys.
I did some comparisons with available specifications as printed in the Yamaha's Service manual Part# LIT-11616-XS-42 which has models from 360 (C-D) through 400's (D-J) and came up with the following. There is not enough of a difference to make up a 11 hp (24%) difference between the models.
The following is a quick review and jumping from page to page is hard on these old eyes, so accuracy is 98%;
compression the @ 9.3 to 1, with only the 400D being 9.2 to 1
Bore stroke same
Intake and Exhaust Valve sizes same
Cam lobes, lift, duration the same
Timing at 10 DBTDC at 1200 RPM same
Carbs had minor difference in pilot jets but the format of document made it difficult to verify this time around. I will research more later.
Exhaust? No way to determine flow restrictions, but again most likely minimal and nothing to cause a 11 hp difference.
Conclusion so far; put on and older carb or do some minor jetting and gain 11 HP.... smile. I really think this is a corporate/printing/reclassification type of error. I still refuse to believe the same engine can loose 11 hp without some sort of governor, rev limiter, ristrickor plate, etc doing so and if there is one where is it?
Be Well
Gil
As you can tell I'm ot on of those "climb the mountain because it's there" kinda guys.