Alittle help with lack of power and popping

[rij1]

So my bike is in the shop and the whole motor was taken apart and Checked, cleaned and put together. Some time before they got my bike it was in another good shop and had the valves adjusted and carbs cleaned. After that the bike was tuned and ran great. Today the shop that has the bike now, said the bike doesn't have power and pops alittle under load. They said the carbs have to be re-jetted. The last shop said it ran great and didn't need anything.
What could be the problem?

[TOOLS1]

Was the air/breather box changed? Did they remove, and then reinstall the carbs?
TOOLS

[rij1]

Its the original air box. The engine was removed, disassembled and rebuilt. So I guess they had to remove the carbs. The bike is still in the shop and their trying to figure it out. But their saying the carbs have to be re-jetted or their dirty.(it ran good before)And the last shop said there was nothing wrong and it ran good.

[shinyribs]

It wouldn't hurt to double check ignition timing and firing order. That can cause what you're describing.

[TOOLS1]

If it ran good before it should run good now! There could be a vacuum leak between the carbs, and head. I think I would take it back to the first shop.
TOOLS

[rij1]

True, get this. when I took my bike there I wanted them to check why it wasnt charging.
They told me it was the regulator/rectifier. (i thought they fixed it).The day I rode the bike to the shop it was popping but that was due to low voltage not the carbs.
I went to the shop today and talked to them and they still say its carb related. So I bring up the reg/rec and they dont know what im talking about and didnt Change it but they said it was bad and quoted me for it. I'm sure its still the cause for my problem. What's your thoughts?

Also, they set the valve lash to .009 on exhaust & .007 on intake. is that ok

[SoonerRon]

Was it popping under acceleration or deceleration? Popping while decelerating can be caused by deteriorated air cutoff valves in the carbs.
The FSM calls for valve clearances of 0.002-0.005" but most agree .005-.006 is better. These engines tend to burn valves when the they are too tight.

[rij1]

It pops(backfires) through load. It idles great. I'm not sure about deceleration.
Should I have them re set the valve lash?

[Lucky 1]

You might as well have given your bike to any 20 year old walking down the street.

I feel sorry for you.

You better get an older experienced Honda
mechanic before this bike becomes worthless.


Modern motorcycle shops just do not understand these bikes.
They know NOTHING about carbs either.
And just because a car mechanic knows about carbs,
has very little to do with these bikes.

[Lucky 1]

You are not telling us nearly enough basic information.

For instance YEAR.
What kind of exhaust?
What kind of intake filtering?

If a shop completely took the engine apart
then it should be like a new engine.

They sound incompetent the way you describe it.

[SoonerRon]

Suprising they chose to set them so loose. The FSM does not specify different clearances for IN and EX so they should be close to the same. If it was my bike I would certainly adjust them. Maybe your shop lacked the correct shims to acheive the proper clearance. Hard to imagine though.

[rij1]

Surprisingly, this shop is very reputable. My signature shows my info. I added 4,1 exhaust and a stock air box to my signature.
I'm going to talk to the owner and see what he says.

[SoonerRon]

CV carbs do not require rejetting when switching to an aftermarket exhaust system as long as you stay with the factory air box and filter. Pods are always a bad idea with these carbs.

[seestheday]

I'm very surprised they set the valve lash to that.  Were they guessing at what it should be?  It's not like the FSM is hard to find.

Was this a Honda dealer?

I could understand them wanting to follow the FSM which most people agree puts the valves a little on the tight side, but I have no idea why they would put them so loose.

[rij1]

No Honda dealer, It is a sales and repair shop.

I did see a Clymer repair manual on the work bench

I'm wondering if they set them with metric measurements instead of inch.


This issue has changed to this posting below. I am still wondering about the valve lash clearance though..

http://honda-cb750-s.456789.n3.nabble.com/Pulse-generator-problems-or-something-else-td4044894.html